Problem 2: We've discussed estimating Xn+ (h21) from (X,..., Xn), but we can apply similar tech- niques to estimate missing values. In this problem, let (X) be a MA(1) process, X = Z+0Z-1, with Z, WN(0,02). Let X3 denote the best (in terms of mean squared error) linear estimate of X3 using the data (X, X2, X4, Xs); see section 2.5.2 in the book for details. 2 a) Find an expression for X b) Using the values o = 1/3 and 0 = 2, what is the mean squared error of the estimate?