A newly dug canal has a trapezoidal cross-section. The mouth of the canal is 2.8m wide, the bottom of the canal is 1.4m wide, and the canal is 1.2m deep. What is its cross-sectional area?
一条新挖的水渠，横截面是梯形．渠口宽2.8m，渠底宽1.4m，渠深1.2m．它的横截面的面积是多少？
<gadget id="calculator">2.8 + 1.4</gadget>
<output>4.2</output>

<gadget id="calculator">1.2 / 2</gadget>
<output>0.6</output>

<gadget id="calculator">4.2 * 0.6</gadget>
<output>2.52</output>

<result>2.52</result>