White pollution has been destroying our living environment. An ordinary plastic bag discarded on the ground covers an area of about 0.04 square meters. If our city has a population of about 500,000, and each person discards a plastic bag, how much area will be polluted?
白色污染一直在破坏我们生活环境，一个普通的塑料袋丢弃在地上占地面积大约是0.04平方米，如果我们的城市大约有人口50万，每人丢弃一个塑料袋，会污染多大面积？
<gadget id="calculator">50 * 10_000</gadget>
<output>500_000</output>

<gadget id="calculator">0.04 * 500_000</gadget>
<output>20_000</output>

<result>20_000</result>