The circumference of the base of a cylinder is 15.7 cm. If the height increases by 2 cm, how many square centimeters does its surface area increase?
一个圆柱的底面周长15.7厘米，若高增加2厘米，它的表面积增加多少平方厘米？
<gadget id="calculator">15.7 * 2</gadget>
<output>31.4</output>

<result>31.4</result>