On the drawing with a scale of 1:500, the side length of a square flower bed is 4 cm. What is the actual area of the flower bed in square meters?
在比例尺是1：500的图纸上，量得一个正方形花坛的边长是4厘米，这个花坛的实际面积是多少平方米．
<gadget id="calculator">20 * 20</gadget>
<output>400</output>

<result>400</result>