Php 使用Laravel雄辩连接连接三个表

这是我的桌子结构

announcement_catagory

 `id`
 `company_id`
 `category_name`
 `employee_id`
 `created_date`

播音员

`id`, 
`company_id`, 
`employee_id`, 
`category_id`,
`title`, 
`announcement`, 
allow_comment`,
announcement_date`,
view_count`,
status`

announcement_comment
    `id`,
    `company_id`, 
    `employee_id`,
    `category_id`,
    `title`,
    `announcement`,
    `allow_comment`,
    `announcement_date`,
    `view_count`,
    `status`

而我的模特们

class Announcement extends BaseClientCompanyModel {

protected $table = "Announcement";

}

class AnnouncementCategory extends BaseClientCompanyModel {

        protected $table = "Announcement_Category";
}

类AnnouncementComment扩展BaseClientCompanyModel{

protected $table = "announcement_comment";

}

我需要得到公告的基础上，公司id与他们的类别和评论的数量，我不知道我应该从哪里开始