A ring with a width of 2 cm and an outer diameter of 1 decimeter, what is the area of the ring?
一个环形，环宽是2厘米，外圆直径是1分米，这个环形的面积是多少？
<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">1 * 5</gadget>
<output>5</output>

<gadget id="calculator">5 ** 2</gadget>
<output>25</output>

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

<gadget id="calculator">25 - 5 - 4</gadget>
<output>16</output>

<gadget id="calculator">3.14 * 16</gadget>
<output>50.24</output>

<result>50.24</result>