The price of domestic refined oil has been lowered, and there is a long queue of vehicles coming to refuel. A certain gas station has two refueling guns to refuel the cars respectively. It takes 7 minutes for car A, 8 minutes for car B, 9 minutes for car C, and 9 minutes for car D. It takes 4 minutes, car E takes 2 minutes, and car F takes 5 minutes. What is the minimum waiting time for refueling?
国内成品油价格下调，前来加油的车辆排起了长队，某加油站有2个加油枪分别给汽车加油，A车要7分钟，B车要8分钟，C车要9分钟，D车要4分钟，E车要2分钟，F车要5分钟，最少加油需等候时间是多少分钟．
<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<gadget id="calculator">2 * 2 * 2</gadget>
<output>8</output>

<gadget id="calculator">2 + 7 + 8 + 4 + 7 + 4 + 5 + 9 + 8 + 5</gadget>
<output>59</output>

<result>59</result>