A cylindrical ventilation pipe with a base circumference of 31.4 cm, its length increases by 2 dm, and its surface area increases by how many square centimeters.
一个底面周长为31.4cm的圆柱形通风管，它的长增加2dm，表面积增加多少平方厘米．
<gadget id="calculator">2 * 10</gadget>
<output>20</output>

<gadget id="calculator">31.4 * 20</gadget>
<output>628</output>

<result>628</result>