I can't solve this problem. Can you explain why? Help me, please.

A linear discrete-time system is defined by y[n] = nx[n -M] -nx[n+ N] where N is a positive integer. A WSS random sequence X[n] with the mean ux[n] = 10 and the autocovariance Kx [(] = 56 [(] is applied as an input to this system. The output of the system is a random sequence Y [n]. (a) Determine the mean My [n]. (b) Determine the crosscorrelation Rxy [m, n]. (c) Determine the crosscorrelation Ryx[m, n]. (d) Determine the autocorrelation Ryy [m, n]. (e) Is the sequence Y [n] WSS? Justify your answer. Explanation: The discrete-time system is linear but not time-invariant. Hence convolution sums cannot be used for system operations. Use the expectation algebra and basic derivations as done in class on linear systems. Again, it would be advantageous to compute covariances first and then correlations. Answers: (a) My [n] = 0, (d) Ry [m, n] = 5mn 28[m - n] - (8[m - n-2N]-8[m - n+2N])