4. Consider a Bayesian network taking the form of a chain of n variables, XI, X2 where each of the X can take on k values. (15 points) ,X a) What is the computational cost of running variable elimination on this network if we eliminate the X, in order i.e., first X1, then X2 and so on)? b) Now take the same chain as in the previous question, but eliminate the X starting from X2, going to X3..X and then back to X1. What is the computational cost of running variable elimination with this ordering