Question 1: (20 pts.)
Consider the discrete-time signals given below:
x1  n   0.5 U  n
n
x2 n  Un  3
x3 n   n n 1
(a) Evaluate the convolution of y1 n  x1 n * x2  n .
(b) Evaluate the convolution of y  n  y1 n * x3  n  .