6. Consider the cascade of three causal rstorder LTI discretetime systems shown below H1(Z) H2(Z) H3(Z) where 1 1 2 1 0.32- 0.4 + z 3 H : H : H : _ 1(2) 1 + 0.521' 2M 1 + 0.4z1' 3(2) 1 + 0.5z1 (a) Determine the transfer function of the overall system as a ration of two polynomials in z'l. (b) Determine the difference equation characterizing the overall system. (0) Develop the realization of the overall system with each section realized in direct form II. (d) Develop a parallel form I realization of the overall system. (e) Determine the impulse response of the overall system in closed form