The radius of a circle is 2 meters, the length of a rectangle is equal to the circumference of the circle, and the width is equal to the diameter of the circle, what is the difference in their areas?
一个圆的半径是2米，一个长方形的长等于圆的周长，宽等于这个圆的直径，它们的面积相差多少？
<gadget id="calculator">2 * 3.14 * 2</gadget>
<output>12.56</output>

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

<gadget id="calculator">12.56 * 4</gadget>
<output>50.24</output>

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

<gadget id="calculator">3.14 * 4</gadget>
<output>12.56</output>

<gadget id="calculator">50.24 - 12.56</gadget>
<output>37.68</output>

<result>37.68</result>