A circular boat on the lake rowed 10m from the shore to the lake, kept 10m equidistant from the lakeshore and rowed for a week, and then returned to the lakeshore and rowed a total of 522.4m. Find the area of the lake?
圆形湖面小船自岸边向湖内划行10m，与湖岸保持10m等距划行一周，然后回到湖岸共划行522.4米，求此湖面积？
<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<gadget id="calculator">522.4 - 20</gadget>
<output>502.4</output>

<gadget id="calculator">2 * 3.14</gadget>
<output>6.28</output>

<gadget id="calculator">502.4 / 6.28</gadget>
<output>80</output>

<gadget id="calculator">80 + 10</gadget>
<output>90</output>

<gadget id="calculator">90 ** 2</gadget>
<output>8_100</output>

<gadget id="calculator">3.14 * 8_100</gadget>
<output>25_434</output>

<result>25_434</result>