The area of a circle formed by two concentric circles with a radius of 12m and a radius of 8m.
由半径是12m和半径是8m的两个同心圆组成的圆环面积．
<gadget id="calculator">12 ** 2</gadget>
<output>144</output>

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

<gadget id="calculator">144 - 64</gadget>
<output>80</output>

<gadget id="calculator">3.14 * 80</gadget>
<output>251.2</output>

<result>251.2</result>