Roll a piece of rectangular cardboard with a length of 31.4 cm and a width of 20 cm into a cylinder with a height of 20 cm. What is the maximum volume in cm**3.
将一张长为31.4cm、宽20cm的长方形硬纸板卷成高为20cm的圆柱，体积最大是多少cm**3．
<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 * 20</gadget>
<output>1_570</output>

<result>1_570</result>