Question Six A first order lag system is described with the following differential equation. Use the equation to determine: (a) The open loop transfer function for the system (4 marks) (b) The closed loop transfer function for a unit negative feedback (4 marks) dy + 5y = x(t),y(0) = 0 dt (c) If the system above is disturbed with a step change of 4 units, x(t) = 4, where t is the time in minutes, determine the closed loop response after 20 minutes (12 marks) =