Write down the transfer function of a third-order system with unity steady-state gain which has a real pole at s = -1 and a pair of complex poles at s = -1 +- ja. Simulate the open-loop step response of the system for 'a' values of 1, 2, 4, and 10, and compare the responses obtained with that of a first order system alone. Use Simulink to do the simulations of the step responses.