We have a batch reactor ( r = -k1) with volume of V1. The concentration entering the batch reactor is Co. The batch reactor is operated from t =0 to t = t1. After that the water exits the batch reactor and enters a PFR (r = -k2C) with volume of V2. The water stays in PFR from t = t1to t = t2. What is the concentration of the chemical leaving PFR?