(a) Define the concept abstraction and why is it important in state description? (b) Considering the following diagram: (i) Employing an A-star search, where L is the goal whereby there is horizontally and vertically movement and the cost to move from one square to the next is 1 while employing Manhattan-distance heuristic. Supposing the start node is S. Calculate the frontier after S is expanded. Include f,g,h values for each node place in the frontier. (ii) Identify all nodes that will be expanded using A-star search