rectangular broad-leaved forest with a length of 500 meters and a width of 20 meters, if each hectare of broad-leaved forest can produce 400 kilograms of oxygen per day, how many kilograms of oxygen can this broad-leaved forest produce per day?
一块长500米，宽20米的长方形阔叶林，如果毎公顷的阔叶林每天能制造400千克氧气，这块阔叶林每天能制造多少千克氧气？
<gadget id="calculator">20 / 10_000</gadget>
<output>1/500 = around 0.002</output>

<gadget id="calculator">500 * (1/500) * 400</gadget>
<output>400</output>

<result>400</result>