The solution to this problem is to generally assign values between 1 and 4 to each of the letters while satisfyingthe condition; each number (1-4) must appear exactly once in each row, column, and 2x2 box, without changingthe numerals that are already in the grid.(a) What is the size of the state space for this CSP? You do not have to consider constraints.(b) List all unary constraints(c) If we choose to assign the first variable using the minimum remaining values (MRV) heuristic, which vari-able(s) would get chosen? List all such variables if there is a tie.(d) Prior to assigning any variables, use both unary constraints and arc consistency due to binary constraintsto reduce the domains of the problem.