In this exercise, we will consider the implementation of search algorithms in Prolog. Suppose that successor (X, Y) is true when state Y is a successor of state X; and that goal (X) is true when X is a goal state. Write a definition for solve (X, P), which means that P is a path (list of states) beginning with X, ending in a goal state, and consisting of sequence of legal steps as defined by successor, You will find that depth-first search the easiest way to do this. How easy would it be to add heuristic search control?