A rectangular channel with unfinished concrete surfaces is to be built to discharge water uniformly at a rate of \(8.5 \mathrm{~m}^{3} / \mathrm{s}\). For the case of best cross section, determine the bottom width of the channel if the available vertical drop is

(a) 1.3 and

(b) \(1.9 \mathrm{~m}\) per km.