If the heuristic being used is the number of tiles out of place, which of the following eight-puzzle will be given priority for further consideration by a heuristic search? a. 1 2 3 4 5 7 8 6 b. 2 3 1 5 6 4 7 8 1 c. 3 4 2 6 7 5 8 1 3 d. 4 2 6 7 5 8