Bake a cake on the stove. Both sides of the cake need to be baked. Each side takes 2 minutes. Only 2 cakes can be placed on the stove at the same time. How long does it take to bake 5 cakes?
在火炉上烤饼，饼的两面都要烤，每烤一面要2分钟，炉上只能同时放2张饼，要烤5张饼，至少需要多少分钟．
<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<gadget id="calculator">2 * 3</gadget>
<output>6</output>

<gadget id="calculator">4 + 6</gadget>
<output>10</output>

<result>10</result>