The following system has input x[n] = 9 + 2cos(n/2) + 3cos(n) and output y[n]: 5y[n] + 3y[n − 1] + y[n − 2] = 7x[n] + 6x[n − 1] − x[n − 2] . Calculate: (a) the frequency response H(e j ), and (b) the output y[n].