To make a cuboid cabinet with a length of 5dm, a width of 4dm, and a height of 2dm, how many dm**2 iron sheets are needed.
制作一个长5dm，宽4dm，高2dm的长方体柜子，需要多少dm**2的铁皮．
<gadget id="calculator">5 * 4</gadget>
<output>20</output>

<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">4 * 2</gadget>
<output>8</output>

<gadget id="calculator">20 + 10 + 8</gadget>
<output>38</output>

<gadget id="calculator">38 * 2</gadget>
<output>76</output>

<result>76</result>