3. Let x(n) = 2"[u(n) - u(n-N)] , which is nonzero between n=0 and n=N-1. (a) Find X(z) and its R.O.C. Remember that x(n) is a causal, finite length sequence. (b) Find X(k), the DFT of x(n). (c) Multiply X(z) by (-.5z)/(-.5z) and give the new X(z) and R.O.C. Is the R.O.C. the same as in part (a) ? (d) If we find x(n) from the X(z) of part (c ), is it the same as in the problem statement ? Why