A ring, the diameter of the big circle is 12 cm, and the diameter of the small circle is 8 cm, what is the area of the ring in cm**2.
一个圆环，大圆直径是12厘米，小圆直径是8厘米，圆环的面积是多少cm**2．
<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<gadget id="calculator">6 ** 2</gadget>
<output>36</output>

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

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

<gadget id="calculator">36 - 16</gadget>
<output>20</output>

<gadget id="calculator">3.14 * 20</gadget>
<output>62.8</output>

<result>62.8</result>