1. The problem statement, all variables and given/known data Problem statement is attached...... 2. Relevant equations my attempt at solution is also attached... 3. The attempt at a solution One of my assumptions was to treat the inlet concentration as a disturbance variable, and inlet flow rate as a manipulated variable......However, as I try to solve for the transfer function, it is becoming highly complicated. I am having to linearize the differential mass balance first. Some of my peers said they avoided this by not including disturbance variables in the transfer function. Which approach is correct?