If the radius of the inner circle of a section of a steel pipe is 5 cm and the thickness is 2 cm, what is the cross-sectional area of the steel pipe?
量得一根钢管截面的内圆半径是5厘米，厚2厘米，钢管截面面积是多少？
<gadget id="calculator">5 + 2</gadget>
<output>7</output>

<gadget id="calculator">7 ** 2</gadget>
<output>49</output>

<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

<gadget id="calculator">49 - 25</gadget>
<output>24</output>

<gadget id="calculator">3.14 * 24</gadget>
<output>75.36</output>

<result>75.36</result>