A waste stream with a flow of 2 m3/s containing a BOD5 of 25 mg/L (k=0.2/d) is discharged to a local river with a flow of 10 m3/s. The BOD5 of the river upstream of the discharge is 0.5 mg/L (k=0.12/d). Assuming the BOD decay constant is 0.18/d for the mixed flows, calculate the BOD5 youd expect in a sample of stream water collected 15 km downstream of the discharge. Assume the mixed flow velocity is 5 km/d and that the BOD test rate constant is 0.22/d (because the BOD test is run at a higher temperature than the stream). (Hint, because k values are different, convert all BOD5 to BODu for calculating BOD values after mixing and decay, and convert BODu back to BOD5 for final answer)