Show how backtracking can be use to solve this problem. To select variables, use the most constrained variable heuristic, breaking ties using the most constraining variable heuristic. If ties still exist, break them alphabetically. To select values, use the least constraining value heuristic. If ties still exist, break them numerically (e. g., 1 before 2). Indicate the first 30 branches visited in the search tree (or stop when the solution is reached). Write them in text form with each branch on one line. For example, suppose we had variables X, Y and Z with domains 0, 1, and constraints X6=Y, Y=Z. The first three branches visited in the search tree should be written as