(a) What is an admissible heuristic function? (2 marks) (b) Why the straight-line distance for each node in a graph to the goal node is an admissitile heuristic function? (2 marks) (c) The graph below represents a problem space. S is the start node and G is the goal node. To the right, three different heuristic functions, h1,h2 and h3, are defined in a table. (i) Which of the heuristics, h1,h2 and h3, are admissible? (2 marks) (ii) What is the final solution path found by using Greedy Search using h3 heuristics? What is the path cost? (2 marks) (iii) What is the final solution path found by using A Search using h3 heuristics? What is the path cost? (2 marks)