If a flower bed with a radius of 3m is built in a circular lawn with a diameter of 10m, what is the remaining area of the lawn?
在一个直径为10m的圆形草地中修一个半径为3m的花坛，剩下草地面积多少．
<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">3.14 * 5 * 5</gadget>
<output>78.5</output>

<gadget id="calculator">3.14 * 3 * 3</gadget>
<output>28.26</output>

<gadget id="calculator">78.5 - 28.26</gadget>
<output>50.24</output>

<result>50.24</result>