cylindrical fiberglass filled with water has a circumference of 12.56 decimeters at the bottom and a height of 8 decimeters. Put a conical iron block into the glass tank, the water is just submerged, and the measured water level rises from the original 4 decimeters to 7 decimeters. Find the volume of this conical iron block.
一个装水的圆柱形玻璃钢，底面周长是12.56分米，高是8分米．将一个圆锥形铁块放入玻璃缸中，水正好淹没，测得水面由原来的4分米上升到7分米．求这个圆锥形铁块的体积．
<gadget id="calculator">12.56 / 3.14 / 2</gadget>
<output>2</output>

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

<gadget id="calculator">7 - 4</gadget>
<output>3</output>

<gadget id="calculator">3.14 * 4 * 3</gadget>
<output>37.68</output>

<result>37.68</result>