A rectangular vegetable field is 20 meters long and 15 meters wide, with an average harvest of 18 kilograms of vegetables per square meter. How many kilograms of vegetables are harvested in this field?
一个长方形菜地，长20米，宽15米，平均每平方米收菜18千克，这块地共收菜多少千克？
<gadget id="calculator">20 * 15</gadget>
<output>300</output>

<gadget id="calculator">300 * 18</gadget>
<output>5_400</output>

<result>5_400</result>