4. This exercise involves designing a heuristic function than is better than the heuristic of Example 6.10.

(a) For each of the forward and regression planners, test how efective each of the individual parts of the heuristic for Example 6.10 is, as well as the maximum. Explain why the results you observed occurred.

(b) Give an admissible heuristic function for the forward planner that expands fewer nodes than the forward planner does with that heuristic.

(c) Give an admissible heuristic function for the regression planner that expands fewer nodes than the regression planner does with that heuristic.

An implementation of the heuristic can be found in stripsHeuristic.py in http://artint.info/AIPython/aipython.zip