If a piece of cylindrical steel with a radius of 5 cm is submerged in a cylindrical bucket, the water level inside the bucket will rise by 7 cm; if the cylindrical steel is exposed to the water surface by 15 cm, the water level will drop by 3 cm. What is the volume of this piece of steel?
如果把一段半径为5厘米的圆柱形钢材浸没在一个圆柱形水桶里，桶里面的水面上升7厘米；如果将圆柱形钢材露出水面15厘米，水面又会下降3厘米．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>