The two pond system is fed by a stream with flow rate $1\mathrm{.}0MGD($million gallons per day$)$

and BOD $($nonconservative pollutant$)$ concentration of $30m\frac{g}{L}.$ The rate of decay of

BOD is $0\mathrm{.}2/$day$.$ The volume of each pond is $5$ million gallons. Assuming complete

mixing within the ponds, find the BOD concentration leaving each pond.