A steel pipe has a circular cross section, an outer diameter of 20cm, an inner diameter of 16cm, and a length of 2m. What is the volume of this steel pipe?
一根钢管，横截面是环形，外直径是20cm，内直径是16cm，管长2m，这根钢管的体积是多少？
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">10 ** 2</gadget>
<output>100</output>

<gadget id="calculator">16 / 2</gadget>
<output>8</output>

<gadget id="calculator">8 ** 2</gadget>
<output>64</output>

<gadget id="calculator">100 - 64</gadget>
<output>36</output>

<gadget id="calculator">2 * 100</gadget>
<output>200</output>

<gadget id="calculator">3.14 * 36 * 200</gadget>
<output>22_608</output>

<result>22_608</result>