If the upper base of a trapezoid is increased by 2 meters and the lower base and height remain the same, its area will increase by 4.8 square meters; if the upper base and lower base remain unchanged and the height is increased by 2 meters, its area will increase by 8.5 square meters. Find the original What is the area of the trapezoid.
一个梯形如果上底增加2米，下底与高不变，它的面积就增加4.8平方米；如果上底与下底不变，高增加2米，它的面积就增加8.5平方米，求原梯形的面积多少．
<gadget id="calculator">4.8 / 2</gadget>
<output>2.4</output>

<gadget id="calculator">8.5 / 2 / 2</gadget>
<output>2.125</output>

<gadget id="calculator">2 * 2.4 * 2 * 2.125</gadget>
<output>20.4</output>

<result>20.4</result>