12.2 A stirred-tank blending system with a bypass stream is shown in Fig. E12.2. The control objective is to control the composition of a key component in the exit stream, x4. The chief disturbance variables are the mass fractions of the key component in the inlet streams, X and x2. Using the following information, discuss which flow rate should be selected as the manipulated variable: (i) inlet flow rate w2, (ii) the bypass fraction f, or (iii) exit flow rate, W4. Your choice should reflect both steady-state and dynamic considerations. in le RO (1 - f)wi x2 X1 wi W2 V fw1 X3 24 SYS W4 W3 lene Figure E12.2