The bus company has three buses that need to be repaired. It takes 40 minutes to fix the first bus, 30 minutes to fix the second bus, and 50 minutes to fix the third bus. If only one car can be repaired, how to arrange the repair order to minimize the total waiting time? What is the minimum sum of waiting times?
公交公司有三辆公交车需要修理，修好第一辆需要40分钟，修好第二辆需要30分钟，修好第三辆需要50分钟．如果只能一辆一辆地修，怎样安排修车顺序，才能使等候时间的总和最少？等候时间的总和最少是多少？
<gadget id="calculator">30 * 3</gadget>
<output>90</output>

<gadget id="calculator">40 * 2</gadget>
<output>80</output>

<gadget id="calculator">90 + 80 + 50</gadget>
<output>220</output>

<result>220</result>