There are enough balls of 10 colors in a vending machine. Xiao Ming wants to buy a pair of balls of the same color. If the unit price of the balls is 2 yuan, then, in order to ensure that Xiao Ming realizes his wish, he will spend at least how much yuan.
一个自动售货机里有足够多的10种颜色的球，小明想买一对同颜色的球，如果球的单价是2元，那么，为了确保小明实现愿望，他至少要花费多少元．
<gadget id="calculator">10 + 1</gadget>
<output>11</output>

<gadget id="calculator">11 * 2</gadget>
<output>22</output>

<result>22</result>