6. (10%) For a binary tree, (a) (6%) Describe the methods to store and traverse a binary tree using (1) array, and (2) structure with pointers. (b) (4%) If a binary tree has L levels (the root is at level 1 and so on) and N nodes, the data in each tree node takes A bytes to store, and a pointer takes B bytes to store. Provide an analysis on under which circumstances that storing a binary tree in an array uses less memory than storing it in a structure with pointers