For each of the following pairs of systems, determine the system function H,(z) and the impulse response h,,[n] for the parallel interconnection of the two systems and likewise H (2) and h[n] for the cascade interconnection. (a) h[n] =a"u[n] and h[n] =a"u[n-1]. (b) h[n] =h[-n] = a"u[n], |a|