A waste having an ultimate BOD of 1,000mg/L is discharged to a river at a rate of 2 m3/s. The river has an ultimate BOD of 10mg/L and is flowing at a rate of 8m/s. Assuming a reaction-rate coefficient of 0.1/ day. The river is flowing at a velocity of 10km/day after the discharge point. a) Calculate BOD5 at point of discharge b) Calculate ultimate BOD 20km downstream c) Calculate BOD_5 20km downstream