The inner diameter of a ring is 8 cm and the outer radius is 10 cm, what is its area in square centimeters?
一个圆环的内圆直径是8厘米，外圆半径是10是厘米，它的面积是多少平方厘米．
<gadget id="calculator">10 ** 2</gadget>
<output>100</output>

<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

<gadget id="calculator">100 - 16</gadget>
<output>84</output>

<gadget id="calculator">3.14 * 84</gadget>
<output>263.76</output>

<result>263.76</result>