After cutting a 20 decimeter long cuboid wood into 3 sections, the surface area increases by 8.4 square decimeters. What is the volume of the original cuboid wood?
把一根长20分米的长方体木料截成3段后，表面积比原来增加了8.4平方分米，原来长方体木料的体积是多少立方分米？
<gadget id="calculator">8.4 / 4</gadget>
<output>2.1</output>

<gadget id="calculator">2.1 * 20</gadget>
<output>42</output>

<result>42</result>