A computer has a circular software, the inner radius is 2 cm, and the outer radius is 3 cm, what is its area?
电脑有一种环形软件，内圆半径是2厘米，外圆半径是3厘米，它的面积是多少．
<gadget id="calculator">9 - 4</gadget>
<output>5</output>

<gadget id="calculator">3.14 * 5</gadget>
<output>15.7</output>

<result>15.7</result>