Water flows in a 5-m-wide rectangular channel made from unfinished concrete with n=0 015. The channel contains a long reach on which Sb is constant at Sb =0 020. At one section, flow is at depth y1 =1 5 m, with speed V1 =4 0m s. Calculate and plot the free surface profile for the first 100 m of the channel, and find the final depth.