After cutting off a small cylinder of 2 decimeters from a 1-meter-long cylinder, the surface area is reduced by 6.28 square decimeters. What is the original volume of the wood in cubic decimeters?
把一根长1米的圆柱体木材截去一段2分米的小圆柱后，表面积减少了6.28平方分米，这根木材原来的体积是多少立方分米．
<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">6.28 / 2 / 3.14 / 4</gadget>
<output>0.25</output>

<gadget id="calculator">3.14 * 0.25 * 1 * 10</gadget>
<output>7.85</output>

<result>7.85</result>