Flow of water takes place in a rectangular channel with b = 4 m, n = 0.012, L = 500 m, S0 = 0.00087. The discharge is 33 m3 /s. At the entrance to the channel, the depth is 0.68 m, and at the downstream end a free-outfall condition exists. Perform a profile synthesis to determine the nature of the water surface and energy grade line.