circular iron plate has an inner diameter of 14 decimeters and an outer diameter of 16 decimeters. What is the area of this circular iron plate?
一个环形铁片，内圆直径是14分米，外圆直径是16分米．这个环形铁片的面积是多少？
<gadget id="calculator">16 / 2</gadget>
<output>8</output>

<gadget id="calculator">8 ** 2</gadget>
<output>64</output>

<gadget id="calculator">14 / 2</gadget>
<output>7</output>

<gadget id="calculator">7 ** 2</gadget>
<output>49</output>

<gadget id="calculator">64 - 49</gadget>
<output>15</output>

<gadget id="calculator">3.14 * 15</gadget>
<output>47.1</output>

<result>47.1</result>