A cylindrical pool filled with water has a bottom circumference of 31.4 meters. After part of the water is used, the water level drops by 40 cm, and the remaining water is exactly (7/8) of the water in the pool. What is the volume of the pool?
一个注满水的圆柱形水池，底面周长为31.4米，用去一部分水后，水面下降40厘米，剩下的水正好是这池水的(7/8)，这个水池容积是多少？
<gadget id="calculator">31.4 / 3.14 / 2</gadget>
<output>5</output>

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

<gadget id="calculator">7 / 8</gadget>
<output>7/8 = around 0.875</output>

<gadget id="calculator">1 - (7/8)</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">40 / (1/8) / 100</gadget>
<output>16/5 = around 3.2</output>

<gadget id="calculator">3.14 * 25 * (16/5)</gadget>
<output>251.2</output>

<result>251.2</result>