4. You are studying a stream that is contaminated with a particular reactive contaminant which follows a zero order reaction process (ie. the reaction rate is independent of the concentration of the contaminant). If you assume plug flow, a velocity of 10 cm/sec, and a zero order reaction rate of 0.5 mg/l min, how far down stream will the concentration be reduced by from 10 mg/L to 1 mg/L? (hint: do a mass balance for the system).