In a cylindrical water storage bucket, if a piece of steel material with a radius of 5 cm is put into the water, the water level in the bucket will rise by 7 cm, and if the steel material is exposed to the water surface by 15 cm, the water in the bucket will drop by 3 cm. What is the volume of this piece of steel?
在一圆柱体储水桶里，如果把一段半径为5厘米的钢材全放入水里，桶里的水面就上升7厘米，如果再将钢材露出水面15厘米，桶里的水就下降3厘米，问这段钢材的体积是多少？
<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">15 / 3</gadget>
<output>5</output>

<gadget id="calculator">3.14 * 25 * 5</gadget>
<output>392.5</output>

<gadget id="calculator">392.5 * 7</gadget>
<output>2_747.5</output>

<result>2_747.5</result>