If a 20 decimeter long cylindrical stick is sawed into three sections and divided into three small cylinders, the surface area increases by 8 square decimeters. What is the original volume of the wooden stick in cubic decimeters?
把20分米长的圆柱形木棒锯成三段，分成三个小圆柱，表面积增加了8平方分米，原来木棒的体积是多少立方分米．
<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<gadget id="calculator">8 / 4</gadget>
<output>2</output>

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

<result>40</result>