Problem $4.$ A stream, with a flow rate of $2$ MGD and with a BOD $($a nonconservative pollutant$)$ concentration of $20m\frac{g}{L},$ flows into a pond with $5$ million gallons of water. That pond has a single stream outlet that flows into a second pond with $3$ million gallons of water and a single outlet. The rate of decay of BOD is $0\mathrm{.}3$ day ${?}^{-1}$ and the growth rate for algae is $0\mathrm{.}2$ day ${?}^{-1}.$ Assuming complete mixing within each pond, find the BOD concentration leaving the first pond, and the concentration of BOD leaving the second pond. $($Assume steady state$)(15$ pts $)$ The other answer I got was wrong so please help!