a$.$ The Angle is $60$ Degrees

b$.$ Determine the depth $($d$)$ of flow, when discharge equal to $15m^3{s}^{-1},$ bed slope $=1$:$2000$

and Manning's $N=0\mathrm{.}020.$

Hint: For most economical trapezoidal section, take half of top width $=$ length of one of

sloping side.

Flow depth y$=$b$($sin$60$degree$)/2(1-$cos$60$degree$)$

Mannings: Q$=1/$n$($A$)($Rh$)^2/3($S$)^1/2$

c$.$ Determine the bottom width of the channel.