A trapezoidal cabbage field has an upper base length of 30m, a lower base length of 45m, and a height of 20m. If 40 kg of cabbage is harvested per square meter, how many kg of cabbage will be harvested in this field?
一块梯形白菜地，上底长30m，下底长45m，高20m，如果每平方米收白菜40千克，这块地共收白菜多少千克？
<gadget id="calculator">30 + 45</gadget>
<output>75</output>

<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">75 * 10</gadget>
<output>750</output>

<gadget id="calculator">40 * 750</gadget>
<output>30_000</output>

<result>30_000</result>