1. Find a closed form expression for the following convolution sum: x[n] = au[n]u[n] 2. Determine the following convolution y[n] = x[n] h[n] where x[n] = 8[n 1] - 28[n+ 1], 3. If y[n] h[n] *x[n], * h[n] = 8[n+ 3] - 8[n] - 8[n-2] where h[n] = {2,-3, 4, 1} and x[n] = {-3, 5, -6, 4}, Determine the value of y[-1] without computing the convolution sum. 4. Evaluate the following sequences: a. autocorrelation sequence rxx (1) of the following sequence x[n] = {2, 0, -1, 6, -3, 2, 0}, b. the cross correlation sequence rxy(1) between the sequences x[n] and y[n] = {8, 2, -7,-3, 0, 1, 1},