A trapezoidal lawn, the upper base is 28 meters long, 12 meters shorter than the lower base, and 40 meters high, what is the area of the grass?
一块梯形草地，上底长28米，比下底少12米，高40米，这块草地的面积是多少？
<gadget id="calculator">28 + 12</gadget>
<output>40</output>

<gadget id="calculator">28 + 40</gadget>
<output>68</output>

<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<gadget id="calculator">68 * 20</gadget>
<output>1_360</output>

<result>1_360</result>