In bioengineering the control of foam is an important task. Foam can lead to drop in selectivity and in the worst case even to contanimation. To this end, it is important to measure the foam level and take counter action if needed. 1. Suggest a measurement principle to detect the foam! 2. To destroy the foam so-called anti-foam agents are pumped into the tank. Please explain why the problem might not instantaneously been solved! 3. Complete the sketch below by labelling the following terms (a) Controlled variable (x) (b) Control variable (u) (c) Reference (w) (d) Disturbance (2) (e) Plant (f) Controller (g) Actuator (h) Sensor bog