The wastewater treatment plant of a paper mill has a volumetric flow rate of $1\mathrm{.}2\frac{m^3}{(s)}$

and an ultimate BOD of $25m\frac{g}{L}.$ This stream is discharged into a river with a volumetric

flow rate of $14\frac{m^3}{(s)}.$ Assuming a constant cross$-$sectional area for the river $(65m^2),$ calculate the

ultimate BOD at a point $8\mathrm{.}5km$ downstream of the river. The deoxygenation constant is $0\mathrm{.}19$

$da{y}^{-1}.$