In the channel whose crosssection is given, the flow rate is $Q=0\mathrm{.}65m\frac{3}{sec},$ the $n$ value is $0\mathrm{.}023$ and the hydraulic slope is $j=0\mathrm{.}0023.$ Determine the water height and average velocity in the channel. $(30p)$

$($Try the values for $y$ between $0\mathrm{.}370-0\mathrm{.}396m.$ According to your $y$ value, calculate the $V$ value.$)$