**Complete this problem in the LANGUAGE SCHEME (R5RS)**

2. (A continuation of the previous problem; pre-, in-, and post-order traversal.) Such trees can be traversed recursively (which you will have done in the solution to your previous problem). In this problem, you will print out the expression associated with a parse tree, using several different conventions for writing arithmetic expressions. There are three conventional orders in which nodes and subtrees can be "visited" during a recursive traversal of a tree. Note that at each node, there three tasks to carry out: visit (in this case, that means print out) the node, traverse the left subtree, and traverse the right subtree. For instance, an inorder traversal of a binary tree wll 1) recursively traverse the left subtree, 2) visit the node, and then 3) recursively traverse the right subtree