A cylinder whose base area remains the same, if the height increases by 4cm, the surface area increases by 125.6cm**2, what is the base area of the cylinder in cm**2?
一个圆柱，它的底面积不变，如果高增加4cm，表面积就增加125.6cm**2，这个圆柱的底面积是多少cm**2．
<gadget id="calculator">125.6 / 4</gadget>
<output>31.4</output>

<gadget id="calculator">31.4 / 3.14 / 2</gadget>
<output>5</output>

<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">3.14 * 25</gadget>
<output>78.5</output>

<result>78.5</result>