The silver part of the disc is a ring, the radius of the inner circle is 2cm, and the radius of the outer circle is 5cm, so what is the area of the silver part in cm**2.
光盘的银色部分是一个圆环，内圆半径是2cm，外圆半径5cm，那么银色部分的面积是多少cm**2．
<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

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

<gadget id="calculator">25 - 4</gadget>
<output>21</output>

<gadget id="calculator">3.14 * 21</gadget>
<output>65.94</output>

<result>65.94</result>