A cylinder with a height of 16 cm is cut into two half cylinders along its diameter. The sum of the surface areas is 640 square centimeters larger than the original surface area. What is the original volume of the cylinder?
一个圆柱高16cm，沿着直径切成两个半圆柱，表面积的和比原来的表面积增加640平方厘米，原来这个圆柱的体积是多少？
<gadget id="calculator">640 / 2 / 16</gadget>
<output>20</output>

<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">10 ** 2</gadget>
<output>100</output>

<gadget id="calculator">3.14 * 100 * 16</gadget>
<output>5_024</output>

<result>5_024</result>