Build a small circular flower bed with a radius of 6 meters in the center of a circular pool. After construction, the width of the water surface is 4 meters. Find the area of the water surface.
在一个圆形水池的中央修建一个半径6米的圆形小花坛，修建后水面宽度是4米．求水面面积为多少．
<gadget id="calculator">6 + 4</gadget>
<output>10</output>

<gadget id="calculator">10 ** 2</gadget>
<output>100</output>

<gadget id="calculator">6 ** 2</gadget>
<output>36</output>

<gadget id="calculator">100 - 36</gadget>
<output>64</output>

<gadget id="calculator">3.14 * 64</gadget>
<output>200.96</output>

<result>200.96</result>