Splitting a 1-meter-long log into two equal halves along its diameter increases the surface area by 0.8 square meters. What is the volume of the original log in square meters?
将一段长1米的圆木沿直径劈成相等的两半，表面积增加了0.8平方米．原来圆木的体积是多少平方米？
<gadget id="calculator">0.8 / 2 / 1</gadget>
<output>0.4</output>

<gadget id="calculator">0.4 / 2</gadget>
<output>0.2</output>

<gadget id="calculator">0.2 ** 2</gadget>
<output>0.04</output>

<gadget id="calculator">3.14 * 0.04 * 1</gadget>
<output>0.1256</output>

<result>0.1256</result>