There is a circular jade disc, the radius r of the inner circle is 2 cm, and the radius R of the outer circle is 3 cm. What is the area of this jade disc in square centimeters?
有一块环形玉璧，内圆半径r为2厘米，外圆半径R为3厘米，这块玉璧的面积是多少平方厘米？
<gadget id="calculator">3 ** 2</gadget>
<output>9</output>

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

<gadget id="calculator">9 - 4</gadget>
<output>5</output>

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

<result>15.7</result>