A channel, $1\mathrm{.}25m-$wide has a straight wall and $V-$shape at the bottom as shown in FIGURE Q$2.$ If $Q=0\mathrm{.}85\frac{m^3}{s},S_0=1$:$1200$ and $C=60\frac{m^{\frac{1}{2}}}{s}.$

a$.$ Compute the depth of $y_2.$

$[3$ marks$]$

b$.$ Calculate the depth of the flow, $y$ measured from the bottom of the channel by using trial and error method.