For a trapezoidal lawn, the sum of the upper and lower bases is 120 cm, and the height is 40 cm. What is the area of the lawn in square centimeters?
一个梯形草坪，上底与下底的和是120厘米，高的长度是40厘米，这个草坪面积是多少平方厘米．
<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<gadget id="calculator">120 * 20</gadget>
<output>2_400</output>

<result>2_400</result>