jQuery：我将如何重新计算下拉列表？

所以我对这类东西是个新手，但我想做一个奇怪的表格。这是一种预订表单，当用户选择新选项时，价格会自动更新

    <div id="base-price">
        <h1>Kosten reis</h1>
    </div><!-- /base-price-->
    <br><br>
    <div id="price-premium">
        <h4>Toeslagen</h4>
        <p><input type="checkbox" value="Crows feet" rel="50">Toeslag hoogseizoen (juli, augustus) <span class="pricing-color">+ 50,00</span></p>
        <p><input type="checkbox" value="Frown lines" rel="40">Toeslag vertrek vrijdag/zaterdag <span class="pricing-color">+ 40,00</span></p>
        <p><input type="checkbox" value="Individual facial line" rel="385">Toeslag 1 persoonskamer/hut <span class="pricing-color">+ 385,00</span></p>
    </div><!-- /price-premium-->
    <br><br>
    <div id="vehicles">
        <h4>Voertuigen</h4>
        <p><input type="checkbox" rel="110">Motor of scooter <span class="pricing-color">+ 110,00</span></p>
        <p><input type="checkbox" rel="130">Motor met zijspan <span class="pricing-color">+ 130,00</span></p>
        <p><input type="checkbox" rel="250">Auto (maximaal 6m lang en 1,85m hoog) <span class="pricing-color">+ 250,00</span></p>
        <p><input type="checkbox" rel="330">Auto (maximaal 6m lang en 2,45m hoog) <span class="pricing-color">+ 330,00</span></p>
    </div><!-- /vehicles-->
    <br><br>
    <div id="extra-spullen">
        <h4>Gewenste merk auto</h4>
        <select>
            <option rel="200" value="volvo">Volvo</option>
            <option rel="300" value="saab">Saab</option>
            <option rel="500" value="mercedes">Mercedes</option>
            <option rel="700" value="audi">Audi</option>
        </select>
    </div><!-- /extra-spullen-->

    <div id="upgrades">
        <h4>Upgraden van hut op ferry</h4>
        <p style="font-style: italic;">prijzen zijn voor retour overtocht per hut.</p>
        <p><input type="checkbox" rel="45">van 2 persoons binnenhut naar 2 persoons zeezichthut (bedden boven elkaar) <span class="pricing-color">+ 45,00</span></p>
        <p><input type="checkbox" rel="96">van 2 persoons binnenhut naar 2 persoons zeezichthut (bedden naast elkaar) <span class="pricing-color">+ 96,00</span></p>
    </div><!-- /upgrades-->
    <br><br>

    <div id="extra">
        <h4>Extra's</h4>
        <p>Off-road experience</p>
        <p><input type="checkbox" rel="360">1 dag off-road training + scenic tour <span class="pricing-color">+ 360</span></p>
        <p><input type="checkbox" rel="630">2 daagse off-road trainig + scenic tour <span class="pricing-color">+ 630,00</span></p>
    </div><!-- /extra-->
    <br><br>

    <div id="price-total">
        <h4>Kosten reis: &euro;<span id="output"></span></h4>
    </div><!-- /price-total-->



</form>
<script src="js/jquery-ui.js"></script>
</div><!-- /wrapper-->

现在它可以很好地使用复选框。但我不知道如何使用我的下拉列表

    <div id="base-price">
        <h1>Kosten reis</h1>
    </div><!-- /base-price-->
    <br><br>
    <div id="price-premium">
        <h4>Toeslagen</h4>
        <p><input type="checkbox" value="Crows feet" rel="50">Toeslag hoogseizoen (juli, augustus) <span class="pricing-color">+ 50,00</span></p>
        <p><input type="checkbox" value="Frown lines" rel="40">Toeslag vertrek vrijdag/zaterdag <span class="pricing-color">+ 40,00</span></p>
        <p><input type="checkbox" value="Individual facial line" rel="385">Toeslag 1 persoonskamer/hut <span class="pricing-color">+ 385,00</span></p>
    </div><!-- /price-premium-->
    <br><br>
    <div id="vehicles">
        <h4>Voertuigen</h4>
        <p><input type="checkbox" rel="110">Motor of scooter <span class="pricing-color">+ 110,00</span></p>
        <p><input type="checkbox" rel="130">Motor met zijspan <span class="pricing-color">+ 130,00</span></p>
        <p><input type="checkbox" rel="250">Auto (maximaal 6m lang en 1,85m hoog) <span class="pricing-color">+ 250,00</span></p>
        <p><input type="checkbox" rel="330">Auto (maximaal 6m lang en 2,45m hoog) <span class="pricing-color">+ 330,00</span></p>
    </div><!-- /vehicles-->
    <br><br>
    <div id="extra-spullen">
        <h4>Gewenste merk auto</h4>
        <select>
            <option rel="200" value="volvo">Volvo</option>
            <option rel="300" value="saab">Saab</option>
            <option rel="500" value="mercedes">Mercedes</option>
            <option rel="700" value="audi">Audi</option>
        </select>
    </div><!-- /extra-spullen-->

    <div id="upgrades">
        <h4>Upgraden van hut op ferry</h4>
        <p style="font-style: italic;">prijzen zijn voor retour overtocht per hut.</p>
        <p><input type="checkbox" rel="45">van 2 persoons binnenhut naar 2 persoons zeezichthut (bedden boven elkaar) <span class="pricing-color">+ 45,00</span></p>
        <p><input type="checkbox" rel="96">van 2 persoons binnenhut naar 2 persoons zeezichthut (bedden naast elkaar) <span class="pricing-color">+ 96,00</span></p>
    </div><!-- /upgrades-->
    <br><br>

    <div id="extra">
        <h4>Extra's</h4>
        <p>Off-road experience</p>
        <p><input type="checkbox" rel="360">1 dag off-road training + scenic tour <span class="pricing-color">+ 360</span></p>
        <p><input type="checkbox" rel="630">2 daagse off-road trainig + scenic tour <span class="pricing-color">+ 630,00</span></p>
    </div><!-- /extra-->
    <br><br>

    <div id="price-total">
        <h4>Kosten reis: &euro;<span id="output"></span></h4>
    </div><!-- /price-total-->



</form>
<script src="js/jquery-ui.js"></script>
</div><!-- /wrapper-->

有人能帮我吗？我试过像“选择选项：选择”之类的东西，但我有点迷路了

    <div id="base-price">
        <h1>Kosten reis</h1>
    </div><!-- /base-price-->
    <br><br>
    <div id="price-premium">
        <h4>Toeslagen</h4>
        <p><input type="checkbox" value="Crows feet" rel="50">Toeslag hoogseizoen (juli, augustus) <span class="pricing-color">+ 50,00</span></p>
        <p><input type="checkbox" value="Frown lines" rel="40">Toeslag vertrek vrijdag/zaterdag <span class="pricing-color">+ 40,00</span></p>
        <p><input type="checkbox" value="Individual facial line" rel="385">Toeslag 1 persoonskamer/hut <span class="pricing-color">+ 385,00</span></p>
    </div><!-- /price-premium-->
    <br><br>
    <div id="vehicles">
        <h4>Voertuigen</h4>
        <p><input type="checkbox" rel="110">Motor of scooter <span class="pricing-color">+ 110,00</span></p>
        <p><input type="checkbox" rel="130">Motor met zijspan <span class="pricing-color">+ 130,00</span></p>
        <p><input type="checkbox" rel="250">Auto (maximaal 6m lang en 1,85m hoog) <span class="pricing-color">+ 250,00</span></p>
        <p><input type="checkbox" rel="330">Auto (maximaal 6m lang en 2,45m hoog) <span class="pricing-color">+ 330,00</span></p>
    </div><!-- /vehicles-->
    <br><br>
    <div id="extra-spullen">
        <h4>Gewenste merk auto</h4>
        <select>
            <option rel="200" value="volvo">Volvo</option>
            <option rel="300" value="saab">Saab</option>
            <option rel="500" value="mercedes">Mercedes</option>
            <option rel="700" value="audi">Audi</option>
        </select>
    </div><!-- /extra-spullen-->

    <div id="upgrades">
        <h4>Upgraden van hut op ferry</h4>
        <p style="font-style: italic;">prijzen zijn voor retour overtocht per hut.</p>
        <p><input type="checkbox" rel="45">van 2 persoons binnenhut naar 2 persoons zeezichthut (bedden boven elkaar) <span class="pricing-color">+ 45,00</span></p>
        <p><input type="checkbox" rel="96">van 2 persoons binnenhut naar 2 persoons zeezichthut (bedden naast elkaar) <span class="pricing-color">+ 96,00</span></p>
    </div><!-- /upgrades-->
    <br><br>

    <div id="extra">
        <h4>Extra's</h4>
        <p>Off-road experience</p>
        <p><input type="checkbox" rel="360">1 dag off-road training + scenic tour <span class="pricing-color">+ 360</span></p>
        <p><input type="checkbox" rel="630">2 daagse off-road trainig + scenic tour <span class="pricing-color">+ 630,00</span></p>
    </div><!-- /extra-->
    <br><br>

    <div id="price-total">
        <h4>Kosten reis: &euro;<span id="output"></span></h4>
    </div><!-- /price-total-->



</form>
<script src="js/jquery-ui.js"></script>
</div><!-- /wrapper-->

小提琴：

    <div id="base-price">
        <h1>Kosten reis</h1>
    </div><!-- /base-price-->
    <br><br>
    <div id="price-premium">
        <h4>Toeslagen</h4>
        <p><input type="checkbox" value="Crows feet" rel="50">Toeslag hoogseizoen (juli, augustus) <span class="pricing-color">+ 50,00</span></p>
        <p><input type="checkbox" value="Frown lines" rel="40">Toeslag vertrek vrijdag/zaterdag <span class="pricing-color">+ 40,00</span></p>
        <p><input type="checkbox" value="Individual facial line" rel="385">Toeslag 1 persoonskamer/hut <span class="pricing-color">+ 385,00</span></p>
    </div><!-- /price-premium-->
    <br><br>
    <div id="vehicles">
        <h4>Voertuigen</h4>
        <p><input type="checkbox" rel="110">Motor of scooter <span class="pricing-color">+ 110,00</span></p>
        <p><input type="checkbox" rel="130">Motor met zijspan <span class="pricing-color">+ 130,00</span></p>
        <p><input type="checkbox" rel="250">Auto (maximaal 6m lang en 1,85m hoog) <span class="pricing-color">+ 250,00</span></p>
        <p><input type="checkbox" rel="330">Auto (maximaal 6m lang en 2,45m hoog) <span class="pricing-color">+ 330,00</span></p>
    </div><!-- /vehicles-->
    <br><br>
    <div id="extra-spullen">
        <h4>Gewenste merk auto</h4>
        <select>
            <option rel="200" value="volvo">Volvo</option>
            <option rel="300" value="saab">Saab</option>
            <option rel="500" value="mercedes">Mercedes</option>
            <option rel="700" value="audi">Audi</option>
        </select>
    </div><!-- /extra-spullen-->

    <div id="upgrades">
        <h4>Upgraden van hut op ferry</h4>
        <p style="font-style: italic;">prijzen zijn voor retour overtocht per hut.</p>
        <p><input type="checkbox" rel="45">van 2 persoons binnenhut naar 2 persoons zeezichthut (bedden boven elkaar) <span class="pricing-color">+ 45,00</span></p>
        <p><input type="checkbox" rel="96">van 2 persoons binnenhut naar 2 persoons zeezichthut (bedden naast elkaar) <span class="pricing-color">+ 96,00</span></p>
    </div><!-- /upgrades-->
    <br><br>

    <div id="extra">
        <h4>Extra's</h4>
        <p>Off-road experience</p>
        <p><input type="checkbox" rel="360">1 dag off-road training + scenic tour <span class="pricing-color">+ 360</span></p>
        <p><input type="checkbox" rel="630">2 daagse off-road trainig + scenic tour <span class="pricing-color">+ 630,00</span></p>
    </div><!-- /extra-->
    <br><br>

    <div id="price-total">
        <h4>Kosten reis: &euro;<span id="output"></span></h4>
    </div><!-- /price-total-->



</form>
<script src="js/jquery-ui.js"></script>
</div><!-- /wrapper-->

HTML的代码：

    <div id="base-price">
        <h1>Kosten reis</h1>
    </div><!-- /base-price-->
    <br><br>
    <div id="price-premium">
        <h4>Toeslagen</h4>
        <p><input type="checkbox" value="Crows feet" rel="50">Toeslag hoogseizoen (juli, augustus) <span class="pricing-color">+ 50,00</span></p>
        <p><input type="checkbox" value="Frown lines" rel="40">Toeslag vertrek vrijdag/zaterdag <span class="pricing-color">+ 40,00</span></p>
        <p><input type="checkbox" value="Individual facial line" rel="385">Toeslag 1 persoonskamer/hut <span class="pricing-color">+ 385,00</span></p>
    </div><!-- /price-premium-->
    <br><br>
    <div id="vehicles">
        <h4>Voertuigen</h4>
        <p><input type="checkbox" rel="110">Motor of scooter <span class="pricing-color">+ 110,00</span></p>
        <p><input type="checkbox" rel="130">Motor met zijspan <span class="pricing-color">+ 130,00</span></p>
        <p><input type="checkbox" rel="250">Auto (maximaal 6m lang en 1,85m hoog) <span class="pricing-color">+ 250,00</span></p>
        <p><input type="checkbox" rel="330">Auto (maximaal 6m lang en 2,45m hoog) <span class="pricing-color">+ 330,00</span></p>
    </div><!-- /vehicles-->
    <br><br>
    <div id="extra-spullen">
        <h4>Gewenste merk auto</h4>
        <select>
            <option rel="200" value="volvo">Volvo</option>
            <option rel="300" value="saab">Saab</option>
            <option rel="500" value="mercedes">Mercedes</option>
            <option rel="700" value="audi">Audi</option>
        </select>
    </div><!-- /extra-spullen-->

    <div id="upgrades">
        <h4>Upgraden van hut op ferry</h4>
        <p style="font-style: italic;">prijzen zijn voor retour overtocht per hut.</p>
        <p><input type="checkbox" rel="45">van 2 persoons binnenhut naar 2 persoons zeezichthut (bedden boven elkaar) <span class="pricing-color">+ 45,00</span></p>
        <p><input type="checkbox" rel="96">van 2 persoons binnenhut naar 2 persoons zeezichthut (bedden naast elkaar) <span class="pricing-color">+ 96,00</span></p>
    </div><!-- /upgrades-->
    <br><br>

    <div id="extra">
        <h4>Extra's</h4>
        <p>Off-road experience</p>
        <p><input type="checkbox" rel="360">1 dag off-road training + scenic tour <span class="pricing-color">+ 360</span></p>
        <p><input type="checkbox" rel="630">2 daagse off-road trainig + scenic tour <span class="pricing-color">+ 630,00</span></p>
    </div><!-- /extra-->
    <br><br>

    <div id="price-total">
        <h4>Kosten reis: &euro;<span id="output"></span></h4>
    </div><!-- /price-total-->



</form>
<script src="js/jquery-ui.js"></script>
</div><!-- /wrapper-->

})

    <div id="base-price">
        <h1>Kosten reis</h1>
    </div><!-- /base-price-->
    <br><br>
    <div id="price-premium">
        <h4>Toeslagen</h4>
        <p><input type="checkbox" value="Crows feet" rel="50">Toeslag hoogseizoen (juli, augustus) <span class="pricing-color">+ 50,00</span></p>
        <p><input type="checkbox" value="Frown lines" rel="40">Toeslag vertrek vrijdag/zaterdag <span class="pricing-color">+ 40,00</span></p>
        <p><input type="checkbox" value="Individual facial line" rel="385">Toeslag 1 persoonskamer/hut <span class="pricing-color">+ 385,00</span></p>
    </div><!-- /price-premium-->
    <br><br>
    <div id="vehicles">
        <h4>Voertuigen</h4>
        <p><input type="checkbox" rel="110">Motor of scooter <span class="pricing-color">+ 110,00</span></p>
        <p><input type="checkbox" rel="130">Motor met zijspan <span class="pricing-color">+ 130,00</span></p>
        <p><input type="checkbox" rel="250">Auto (maximaal 6m lang en 1,85m hoog) <span class="pricing-color">+ 250,00</span></p>
        <p><input type="checkbox" rel="330">Auto (maximaal 6m lang en 2,45m hoog) <span class="pricing-color">+ 330,00</span></p>
    </div><!-- /vehicles-->
    <br><br>
    <div id="extra-spullen">
        <h4>Gewenste merk auto</h4>
        <select>
            <option rel="200" value="volvo">Volvo</option>
            <option rel="300" value="saab">Saab</option>
            <option rel="500" value="mercedes">Mercedes</option>
            <option rel="700" value="audi">Audi</option>
        </select>
    </div><!-- /extra-spullen-->

    <div id="upgrades">
        <h4>Upgraden van hut op ferry</h4>
        <p style="font-style: italic;">prijzen zijn voor retour overtocht per hut.</p>
        <p><input type="checkbox" rel="45">van 2 persoons binnenhut naar 2 persoons zeezichthut (bedden boven elkaar) <span class="pricing-color">+ 45,00</span></p>
        <p><input type="checkbox" rel="96">van 2 persoons binnenhut naar 2 persoons zeezichthut (bedden naast elkaar) <span class="pricing-color">+ 96,00</span></p>
    </div><!-- /upgrades-->
    <br><br>

    <div id="extra">
        <h4>Extra's</h4>
        <p>Off-road experience</p>
        <p><input type="checkbox" rel="360">1 dag off-road training + scenic tour <span class="pricing-color">+ 360</span></p>
        <p><input type="checkbox" rel="630">2 daagse off-road trainig + scenic tour <span class="pricing-color">+ 630,00</span></p>
    </div><!-- /extra-->
    <br><br>

    <div id="price-total">
        <h4>Kosten reis: &euro;<span id="output"></span></h4>
    </div><!-- /price-total-->



</form>
<script src="js/jquery-ui.js"></script>
</div><!-- /wrapper-->

演示：注意：我添加了“请选择”选项值：0，稍微更方便用户

    <div id="base-price">
        <h1>Kosten reis</h1>
    </div><!-- /base-price-->
    <br><br>
    <div id="price-premium">
        <h4>Toeslagen</h4>
        <p><input type="checkbox" value="Crows feet" rel="50">Toeslag hoogseizoen (juli, augustus) <span class="pricing-color">+ 50,00</span></p>
        <p><input type="checkbox" value="Frown lines" rel="40">Toeslag vertrek vrijdag/zaterdag <span class="pricing-color">+ 40,00</span></p>
        <p><input type="checkbox" value="Individual facial line" rel="385">Toeslag 1 persoonskamer/hut <span class="pricing-color">+ 385,00</span></p>
    </div><!-- /price-premium-->
    <br><br>
    <div id="vehicles">
        <h4>Voertuigen</h4>
        <p><input type="checkbox" rel="110">Motor of scooter <span class="pricing-color">+ 110,00</span></p>
        <p><input type="checkbox" rel="130">Motor met zijspan <span class="pricing-color">+ 130,00</span></p>
        <p><input type="checkbox" rel="250">Auto (maximaal 6m lang en 1,85m hoog) <span class="pricing-color">+ 250,00</span></p>
        <p><input type="checkbox" rel="330">Auto (maximaal 6m lang en 2,45m hoog) <span class="pricing-color">+ 330,00</span></p>
    </div><!-- /vehicles-->
    <br><br>
    <div id="extra-spullen">
        <h4>Gewenste merk auto</h4>
        <select>
            <option rel="200" value="volvo">Volvo</option>
            <option rel="300" value="saab">Saab</option>
            <option rel="500" value="mercedes">Mercedes</option>
            <option rel="700" value="audi">Audi</option>
        </select>
    </div><!-- /extra-spullen-->

    <div id="upgrades">
        <h4>Upgraden van hut op ferry</h4>
        <p style="font-style: italic;">prijzen zijn voor retour overtocht per hut.</p>
        <p><input type="checkbox" rel="45">van 2 persoons binnenhut naar 2 persoons zeezichthut (bedden boven elkaar) <span class="pricing-color">+ 45,00</span></p>
        <p><input type="checkbox" rel="96">van 2 persoons binnenhut naar 2 persoons zeezichthut (bedden naast elkaar) <span class="pricing-color">+ 96,00</span></p>
    </div><!-- /upgrades-->
    <br><br>

    <div id="extra">
        <h4>Extra's</h4>
        <p>Off-road experience</p>
        <p><input type="checkbox" rel="360">1 dag off-road training + scenic tour <span class="pricing-color">+ 360</span></p>
        <p><input type="checkbox" rel="630">2 daagse off-road trainig + scenic tour <span class="pricing-color">+ 630,00</span></p>
    </div><!-- /extra-->
    <br><br>

    <div id="price-total">
        <h4>Kosten reis: &euro;<span id="output"></span></h4>
    </div><!-- /price-total-->



</form>
<script src="js/jquery-ui.js"></script>
</div><!-- /wrapper-->