Four input-output pairs of a particular system S are specified in Figure P2.28-1:

(a)  Can system S be time-invariant? Explain.

(b)  Can system S be linear? Explain.

(c)  Suppose (2) and (3) are input-output pairs of a particular system S ₂ , and the system is known to be LTI. What is h[n], the impulse response of the system?

(d)  Suppose (1) is the input-output pair of an LTI system S ₃ . What is the output of this system for the input in Figure P2.28-2:

(1) S 012 0 123 4 (2) L.L 012 012345 1 1 11 012 (3) 0 12 3 45 1 1 (4) 0 12345 Figure P2.28-1 # 2 2 2 . 0 1 2 3 4 Figure P2.28-2