Suppose that we want to design a Discrete-Time LTI system which has the property that if the input is ????[????] = (1 2)???? ????[????] ? 1 4 (1 2)?????1 ????[???? ? 1] then the output is ????[????] = (1 3)???? ????[????]. a) Find the frequency response (???? ????????????) of the discrete-time LTI system. b) Find the impulse response ?[????] of the discrete-time LTI system (using the partial fraction expansion method). Supplementary: Fourier transform pairs: ????????????[????] ? 1 1?????????????????? for | |???? < 1