The two pond system shown in the figure below is fed by a stream with a flowrate of 1.0 MGD and a BOD concentration of 20 mg/l. The rate of decay of BOD is 0.39/day. The volume of the first pond is 5.0 million gallons, and the second pond is 3.0 million gallons. Assuming complete mixing within each pond, find the BOD concentration leaving each pond?