design a concrete (n = 0.013) channel that will convey 50,000 GPM. It is to be a trapezoidal in cross section with a bottom width of 7.5 feet. The side slopes are to be 1.33:1 (H:V) and it is desired to have the depth of flow constant at 2.0 feet. How many inches should the channel drop in 350 feet of length?