3. (a). The liquid level in a two-tanks-in-serics system is to be controlled using a simple proportional controller. Both tanks have unity gain with time constants 1min, and 1/2min. respectively. The liquid level measuring device that provides feedback to the controller is also unity gain with time-constant 1/3min. Draw a block diagrain of the control system. Using the Routh test, find the range of values of controller gain Kc, for which the control system is stable