Compute the flow rate $($cfs$)$ in the following open channel assuming a uniform flow for a water depth $($y$)$ of $7$

$ft$ : Manning's roughness $=0\mathrm{.}014,$ river bed slope $=0\mathrm{.}0028,b_1=b_3=15ft,b_2=26ft,$ and $y_2=3ft.$

Enter the answer as an integer $($like $987)$ without unit.