uniform wooden rod has a cross-section of a circle with a diameter of 4 cm. After cutting it into two sections, the sum of the surface areas is 75.36 square centimeters. Find the volume of the original wooden rod?
一根均匀的木棒，横截面是直径4厘米的圆，把它截成2段后，表面积的和为75.36平方厘米，求原来木棒的体积？
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

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

<gadget id="calculator">3.14 * 4 * 4</gadget>
<output>50.24</output>

<gadget id="calculator">75.36 - 50.24</gadget>
<output>25.12</output>

<gadget id="calculator">3.14 * 4</gadget>
<output>12.56</output>

<gadget id="calculator">25.12 / 12.56</gadget>
<output>2</output>

<gadget id="calculator">3.14 * 4 * 2</gadget>
<output>25.12</output>

<result>25.12</result>