The cross-section of a cannel is a trapezium in shape. If the cannel is 12 m wide at the top and 5 m wide at the bottom and the area of cross-section is 344 sq m, the depth of cannel is?  Choose the correct choice from the following options.
A) 39 B) 28 C) 27 D) 40 E) 71
1/2 * d (12 + 5) = 344   d = 40   Answer: 40
<result>D</result>
The cross-section of a cannel is a trapezium in shape. If the cannel is 12 m wide at the top and 5 m wide at the bottom and the area of cross-section is 344 sq m, the depth of cannel is?