A cylindrical piece of wood, 2 meters long, is cut vertically along one of its diameters into two equal pieces, and the surface area increases by 40dm**2. What is the volume of this piece of wood?
一个圆柱形的木料，长2米，沿它的一条直径垂直切开分成相等的两块，表面积增加40dm**2，这块木料的体积是多少．
<gadget id="calculator">2 * 10</gadget>
<output>20</output>

<gadget id="calculator">40 / 2 / 20 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) ** 2</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">3.14 * (1/4) * 20</gadget>
<output>15.7</output>

<result>15.7</result>