9. A plug flow reactor is operating at steady state with a zero order reaction and an effluent concentration of 10 mg/L. The hydraulic residence time is 2 hours. At

time zero,receives a step increase that doubles the influent concentration. What is the effluentconcentration at t= 1 hour?the reactor a) 0 mg/L b) 5 mg/L c) 10 mg/L d) 15 mg/L e) 20 mg/L