#$8.$ A rectangular channel has a $20$ ft width and a roughness coefficient, n $=$

$0\mathrm{.}015.$

a$.$ Determine the normal slope at a normal depth of $1\mathrm{.}23$ ft$.$ when the

discharge is $200$ cfs$.$

b$.$ Determine the critical slope and the corresponding normal depth

when the discharge is $200$ cfs$.$

c$.$ Determine the critical slope at the normal depth of $1\mathrm{.}23$ ft$,$ and

compute the corresponding discharge.