The diameter of a circular lawn is 80 meters, and a 10-meter-wide asphalt road is built around the lawn. What is the area of this road in m**2.
一个圆形草坪的直径是80米，在草坪的周围修一条10米宽的柏油马路，这条路的面积是多少m**2．
<gadget id="calculator">80 / 2</gadget>
<output>40</output>

<gadget id="calculator">40 + 10</gadget>
<output>50</output>

<gadget id="calculator">50 ** 2</gadget>
<output>2_500</output>

<gadget id="calculator">3.14 * 2_500</gadget>
<output>7_850</output>

<gadget id="calculator">40 ** 2</gadget>
<output>1_600</output>

<gadget id="calculator">3.14 * 1_600</gadget>
<output>5_024</output>

<gadget id="calculator">7_850 - 5_024</gadget>
<output>2_826</output>

<result>2_826</result>