96 PART 2 LINEAR OPEN-LOOP SYSTEMS 4.17. A simple mixing process follows first-order behavior. A 200-gal mixing tank process, initially at steady state, is shown in Fig. P4-17. At time t=0, the inlet flow is switched from 5\% salt to freshwater. What does the inlet flow rate need to be to reduce the exit concentration to less than 0.5% in 30min