There is a kind of cell that changes from 1 to 2 every 10 minutes. After 40 minutes, how many cells will become of this kind of cell?
有一种细胞，每10分钟就由1个变成2个，这种细胞经过40分钟后，变成多少个细胞．
<gadget id="calculator">2 * 2 * 2 * 2</gadget>
<output>16</output>

<result>16</result>