Consider the FIR filter
y(n) = x(n) + x(n – 4)
(a) Compute and sketch its magnitude and phase response.
(b) Compute its response to the input
x(n) = cos π/2n + cos π/4n -∞ < n < ∞
(c) Explain the results obtained in part (b) in terms of the magnitude and phase responses obtained in part (a).