circular fish pond has a radius of 20 meters, and there is a circular island in the middle with a diameter of 6 meters. What is the water surface area of this fish pond?
一个圆形鱼池半径是20米，它的中间有一个圆形小岛，直径是6米，这个鱼池水面面积是多少？
<gadget id="calculator">20 ** 2</gadget>
<output>400</output>

<gadget id="calculator">6 / 2</gadget>
<output>3</output>

<gadget id="calculator">3 ** 2</gadget>
<output>9</output>

<gadget id="calculator">400 - 9</gadget>
<output>391</output>

<gadget id="calculator">3.14 * 391</gadget>
<output>1_227.74</output>

<result>1_227.74</result>