A circular swimming pool has a bottom circumference of 31.4 meters and a pool depth of 0.8 meters. What is its area?
一个圆形游泳池，底面周长是31.4米，池深是0.8米，它的占地面积是多少．
<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>