The sum of the upper and lower bases of a trapezoid is 4.2m, and the height is 3.5m. What is the area of the parallelogram formed by such two trapezoids in m**2.
一个梯形的上、下底之和是4.2m，高是3.5m，由这样的两个梯形组成的平行四边形的面积是多少m**2．
<gadget id="calculator">3.5 / 2</gadget>
<output>1.75</output>

<gadget id="calculator">4.2 * 1.75 * 2</gadget>
<output>14.7</output>

<result>14.7</result>