If the inner radius of a ring is 14 cm and the outer radius is 18 cm, what is the area of the ring?
一个环形内圆半径为14厘米，外圆半径为18厘米，环形面积是多少π
<gadget id="calculator">18 ** 2</gadget>
<output>324</output>

<gadget id="calculator">14 ** 2</gadget>
<output>196</output>

<gadget id="calculator">324 - 196</gadget>
<output>128</output>

<result>128</result>