The radius of the trunk's cross-section is 22 cm, and the bark is 2 cm thick. What is the cross-sectional area of available wood for the trunk?
树干横截面的半径为22厘米，树皮厚2厘米，树干可用木料的横截面积是多少？
<gadget id="calculator">22 - 2</gadget>
<output>20</output>

<gadget id="calculator">20 ** 2</gadget>
<output>400</output>

<gadget id="calculator">3.14 * 400</gadget>
<output>1_256</output>

<result>1_256</result>