A canal has a trapezoidal cross section, with a mouth width of 4.2 meters, a canal bottom width of 3.8 meters, and a canal depth of 2.6 meters. What is the cross-sectional area of this canal in square meters?
一条水渠横截面是梯形，渠口宽4.2米，渠底宽3.8米，渠深2.6米，这个水渠的横截面的面积是多少平方米．
<gadget id="calculator">4.2 + 3.8</gadget>
<output>8</output>

<gadget id="calculator">2.6 / 2</gadget>
<output>1.3</output>

<gadget id="calculator">8 * 1.3</gadget>
<output>10.4</output>

<result>10.4</result>