Find the impulse response h[n] for each of the causal LTI discrete-time systems satisfying the following difference equations and indicate whether each system is a FIR or an IIR system.
(a) y [n] = x [n] - 2 x [n - 2] + x [n - 3]
(b) y [n] + 2 y [n - 1] = x [n] + x [n - 1]
(c) y [n] - !y [n - 2] = 2 x [n] - x [n - 2]