If a 5-meter-long log is cut into four small logs, the surface area increases by 12 square decimeters. What is the volume of this log in cubic decimeters?
把一根5米长的圆木截成四段小圆木，表面积增加了12平方分米，原来这根圆木的体积是多少立方分米．
<gadget id="calculator">12 / 6</gadget>
<output>2</output>

<gadget id="calculator">2 * 5 * 10</gadget>
<output>100</output>

<result>100</result>