A forest is 30 meters long and 20 meters wide. A forest of 1 square meter produces about 3 kilograms of oxygen per month. How many kilograms of oxygen can this forest produce per month?
一片树林长30米，宽20米．1平方米树林每月大约制造氧气3千克，这片树林每月大约能制造氧气多少千克？
<gadget id="calculator">30 * 20 * 3</gadget>
<output>1_800</output>

<result>1_800</result>