Q$6$a$.$ Assuming the side slope $1$:$1,$ find the bed width $B$ and the depth of flow $D$ of an irrigation canal to carry and discharge of $21\frac{m^3}{s}$ with a velocity of $0\mathrm{.}75\frac{m}{s}.$ bed slope is $1$:$5000$ and values of Chezy's constant C$=42.$