It is desired to control the exit concentration of $c_3$ of the liquid blending system shown in th below.

$($a$)$ What are the controlled, manipulated and disturbance variables?

$($b$)$ Draw a block diagram for the process. You may assume that both the inlet flow rate $q_1$ inlet composition $c_1$ are disturbances

$($c$)$ Modify the existing figure by implementing a feedforward control strategy assuming that th composition $c_1$ is the disturbance variable.