Consider three heuristic functions generated from the following relaxed problems for the 15-puzzle:
1. A tile can move from square A to square B if A is adjacent to B.
2. A tile can move from square A to square B if B is blank.
3. A tile can move from square A to square B if A is adjacent to B.
The function from problem (1) is the Manhattan-distance heuristic, the function from problem (2) is the Gaschnig's heuristic, and the function from problem (3) gives the number of misplaced tiles. Compare these three heuristic functions by measuring the execution time of the 15-puzzle program.