A rectangular swimming pool is built in the middle of a trapezoidal lawn with an upper base of 40 meters, a lower base of 70 meters and a height of 30 meters. It is known that the swimming pool is 30 meters long and 15 meters wide. What is the area of the grass in square meters?
在一块上底是40米，下底是70米，高30米的梯形草地中间修建一个长方形游泳池，已知游泳池的长30米、宽15米，请问草地的面积是多少平方米？
<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>