Uncle Wang has contracted a circular pond, and (1/5) of the pond is stocked with mussels. Every morning, he spends about 15.7 minutes patrolling the pond at a speed of 40 meters per minute. Question: How many square meters does Uncle Wang stock up on mussels?
王叔叔承包了一个圆形池塘，池塘的(1/5)放养河蚌，每天早上，他都要花约15.7分钟，以每分钟40米的速度沿池塘边巡视一圈．问：王叔叔放养的河蚌有多少平方米？
<gadget id="calculator">15.7 * 40</gadget>
<output>628</output>

<gadget id="calculator">628 / 3.14 / 2</gadget>
<output>100</output>

<gadget id="calculator">100 ** 2</gadget>
<output>10_000</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">3.14 * 10_000 * (1/5)</gadget>
<output>6_280</output>

<result>6_280</result>