How many square decimeters are needed to make a pair of cuboid water tanks without a cover whose bottom side length is 2 decimeters and whose height is 10 decimeters?
做一对底面边长是2分米，高是10分米的无盖的长方体水箱，至少需要多少平方分米．
<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<gadget id="calculator">2 * 10 * 4</gadget>
<output>80</output>

<gadget id="calculator">4 + 80</gadget>
<output>84</output>

<result>84</result>