A log with a length of 5 meters is cut into two cylinders of the same size, and the surface area increases by 40 square centimeters. What is the original volume of the log in cubic centimeters?
一根长5米的圆木，截成两同样大小的圆柱后，表面积增加40平方厘米，这根圆木原来的体积是多少立方厘米．
<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<gadget id="calculator">5 * 100</gadget>
<output>500</output>

<gadget id="calculator">20 * 500</gadget>
<output>10_000</output>

<result>10_000</result>