a$)(8$ marks$)$ Suppose that each node of a binary tree is defined as a class with three properties: Left, Right, and Element $($which is an integer$).$Complete the body of the following recursive method which returns the sum of the leaf node values of the binary tree rooted at n$.$public int LeafSum $($Node n$)\{...\}$b$)(2$ marks$)$ State the type of traversal used in part a$).$c$)(2$ marks$)$ The reconstruction of a unique binary tree requires the infix traversal of its nodes $($values$)$ plus either its prefix or postfix traversal. Show why this combination of two traversals is required.