There is only one chef in the star milk cake shop to make cakes. At this time, three customers came to the store at the same time to make birthday cakes. Due to the different types of birthday cakes to be processed, customer A needs to make 4 minutes, customer B needs to make 9 minutes, and customer C needs to make 6 minutes. How to arrange their order so that the sum of the waiting time of these three customers is the least? What is the minimum total waiting time?
星星奶糕店里只有一位师傅做蛋糕．这时店里同时来了三位顾客做生日蛋糕．由于加工的生日蛋糕型号不同，甲顾客的需要做4分钟，乙顾客的需要做9分钟，丙顾客的需要做6分钟．怎样安排他们的顺序才能使这三位顾客等待时间的总和最少呢？等待总时间最少多少分钟？
<gadget id="calculator">4 + 6</gadget>
<output>10</output>

<gadget id="calculator">4 + 6 + 9</gadget>
<output>19</output>

<gadget id="calculator">4 + 10 + 19</gadget>
<output>33</output>

<result>33</result>