There is a trapezoidal land, the upper base is 40 meters long, the lower base is 70 meters long, and the height is 30 meters. A row of factory buildings with a length of 30 meters and a width of 15 meters is to be built in the middle of the land, and the rest of the land is planted with lawn. The area of the lawn is How many?
有一块梯形地，上底长40米，下底长70米，高30米，要在这块地中间建一排长30米，宽15米的厂房，其余的地种草坪，草坪的面积是多少？
<gadget id="calculator">40 + 70</gadget>
<output>110</output>

<gadget id="calculator">30 / 2</gadget>
<output>15</output>

<gadget id="calculator">110 * 15</gadget>
<output>1_650</output>

<gadget id="calculator">30 * 15</gadget>
<output>450</output>

<gadget id="calculator">1_650 - 450</gadget>
<output>1_200</output>

<result>1_200</result>