If the circumference of a circle is 314 cm, what is the area of the circle?
已知一个圆的周长是314cm，那么这个圆的面积是多少．
<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

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

<result>78.5</result>