A square log with a length of 20dm, after sawing it into 3 sections, the surface area increases by 8 square decimeters, what is the volume of this square log in cubic decimeters?
一根长20dm的方木，把它锯成3段后，表面积增加了8平方分米，这根方木的体积是多少立方分米．
<gadget id="calculator">8 / 4</gadget>
<output>2</output>

<gadget id="calculator">2 * 20</gadget>
<output>40</output>

<result>40</result>