6. Define a treeNode class for tree nodes that each consists of following 4 fields: parent leftChild rightChild data 7. Following the above node definition, define and implement a binary tree class with necessary access methods for the 4-field treeNodes, for example, setXXX, getXXX, isEmpty, etc.. 8. Write a method that takes two binary trees t1, t2 and a binary tree node v as the arguments. It constructs and returns a new binary tree that has v as its root and whose left subtree is t1 and whose right subtree is t2. Both tl and t2 should be empty on completion of the execution