Let us consider a process consisting of a linear trend with an additional, serially correlated noise Bo+Bit + wt + Wt-1; t = = xt = 0, 1, 2, . . . , where {w} is a white noise with zero mean and variance o, and o and are some fixed constants. (a) Prove that {x} is not stationary. (b) Take the first difference yt = xt = xt - Xt1, t = 1,2,.... Is {yt} stationary? Explain. If so, compute the mean and autocorrelation function.