I need detailed solution please $,$ Problem $3$: Assignment

A grass$-$lined drainage channel is to carry a discharge of $2000$ cfs at a

maximum velocity of $4\mathrm{.}0fps.$ The side slopes of the channel will be $4$:$1$ and

the longitudinal slope of the channel will be $0\mathrm{.}001.$ Design the channel for

Manning's $n$ values of $0\mathrm{.}03$ and $0\mathrm{.}035.$

Answer: for $n=0\mathrm{.}03,y=4\mathrm{.}9ft,Bo=83ft$ and $FB=3\mathrm{.}1ft$

for $n=0\mathrm{.}035,y=7\mathrm{.}7ft,Bo=34\mathrm{.}2ft$ and $FB=3\mathrm{.}9ft$