Aunt Zhang, Aunt Li and Uncle Wang go shopping in the supermarket. They line up at the same payment gate at the same time. Aunt Zhang takes 1 minute to pay, Aunt Li takes 4 minutes to pay, and Uncle Wang takes 2 minutes to pay. How to arrange them to pay? What order can minimize the sum of the waiting time of the three people?
张大妈、李阿姨和王大爷去超市购物，他们同时排在一个交款口，张大妈交款用1分钟，李阿姨交款用4分钟，王大爷交款用2分钟，怎样安排他们交款的顺序可以使三人等待的时间之和最少？
<gadget id="calculator">2 + 1</gadget>
<output>3</output>

<gadget id="calculator">1 + 2 + 4</gadget>
<output>7</output>

<gadget id="calculator">1 + 3 + 7</gadget>
<output>11</output>

<result>11</result>