Given that the diameter of the base of the cylinder is 4 decimeters and the height is 5 times the diameter, find its volume.
已知圆柱的底面直径是4分米，高是直径的5倍，求它的体积．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">4 * 5</gadget>
<output>20</output>

<gadget id="calculator">3.14 * 4 * 20</gadget>
<output>251.2</output>

<result>251.2</result>