The cross-section of a canal is trapezoidal, the mouth of the canal is 2.5 meters wide, the bottom of the canal is 1.5 meters wide, and the canal is 0.8 meters deep. What is the area of this cross-section?
一个水渠的横截面是梯形，渠口宽2.5米，渠底宽1.5米，渠深0.8米，这个横截面的面积是多少？
<gadget id="calculator">2.5 + 1.5</gadget>
<output>4</output>

<gadget id="calculator">0.8 / 2</gadget>
<output>0.4</output>

<gadget id="calculator">4 * 0.4</gadget>
<output>1.6</output>

<result>1.6</result>