The cross section of a canal is trapezoidal, the width of the mouth is 2.5m, the width of the bottom is 1.4m, and the depth is 2m. What is the area of the cross section of the canal?
一条水渠的横截面是梯形，渠口宽是2.5m，渠底宽是1.4m，渠深为2m，水渠的横截面的面积是多少？
<gadget id="calculator">2.5 + 1.4</gadget>
<output>3.9</output>

<gadget id="calculator">2 / 2</gadget>
<output>1</output>

<gadget id="calculator">3.9 * 1</gadget>
<output>3.9</output>

<result>3.9</result>