With an 8m long rope, the remaining 46.4cm is wrapped around the tree 4 times. What is the cross-sectional area of the tree here?
用8m长的绳子，绕树缠了4圈还余46.4cm，这树此处的横截面积有多大？
<gadget id="calculator">8 * 100</gadget>
<output>800</output>

<gadget id="calculator">800 - 46.4</gadget>
<output>753.6</output>

<gadget id="calculator">753.6 / 4 / 3.14 / 2</gadget>
<output>30</output>

<gadget id="calculator">30 ** 2</gadget>
<output>900</output>

<gadget id="calculator">3.14 * 900</gadget>
<output>2_826</output>

<result>2_826</result>