For a given effluent-stream combination, say values of BOD reaction rate and stream reaeration rate are 0.26 and 0.42 per day, respectively and given that initial dissolved oxygen (DO) deficit is 2 mg/L with ultimate BOD of the mixture equals to 18 mg/L, discuss the approach for calculating time (say t) since mixing of effluent with stream water after which DO deficit becomes 1% of the initial DO deficit? [5 points]