There are 3 trucks unloading at the supermarket in the central building at the same time, and they can only unload the goods one by one. It takes 40 minutes for truck A to be unloaded, 35 minutes for truck B to be unloaded, and 15 minutes for truck C to be unloaded. It takes 3 trucks to wait. The sum of the time is the least, what order should be loaded? What is the minimum time required?
中枢大厦超市同时来了3辆货车卸货，只能一车一车地卸货，甲车卸完需40分钟，乙车卸完需35分，丙车卸完需15分钟，要使3辆车等候时间的总和最少，应该按怎样的顺序装车？最少需要多少时间？
<gadget id="calculator">15 * 3</gadget>
<output>45</output>

<gadget id="calculator">35 * 2</gadget>
<output>70</output>

<gadget id="calculator">45 + 70 + 40</gadget>
<output>155</output>

<result>155</result>