A piece of cuboid steel, its cross-sectional area is 10cm**2, if it is cut into three sections, how much does the surface area increase by cm**2?
一段长方体钢材，它的横截面积是10cm**2，把它截成三段，表面积增加了多少cm**2．
<gadget id="calculator">4 * 10</gadget>
<output>40</output>

<result>40</result>