6. A rule-based expert system has the following rules in its knowledge base. Rule 1: Y & D -> Z Rule 2: X & B & E-> Y Rule 3: A -> X Rule 4: C -> L Rule 5: L & M -> N (1) Explain briefly what are forward chaining and backward chaining. (2) Assuming the initial database of the expert system contains facts A, B, C, D and E, describe how to infer conclusion Z using forward chaining and backward chaining respectively.