If a log 4 meters long is cut into three pieces, the surface area increases by 8 square decimeters, what is the original volume of the log
把一根4米长的圆木截成三段，表面积增加8平方分米，这根圆木的体积原来是多少
<gadget id="calculator">8 / 4</gadget>
<output>2</output>

<gadget id="calculator">4 * 10</gadget>
<output>40</output>

<gadget id="calculator">2 * 40</gadget>
<output>80</output>

<result>80</result>