The following tree is used in this question: consider it as an AVL tree. a. Verify that the tree above is a valid AVL tree, by describing the required properties of an AVL tree. (Write about 3 lines.) b. What are the heights of each node of the tree, according to the AVL definition of height? c. Which nodes would be assigned the labels x, y, z in inserting the value 8 into the above tree? d. Insert the value 8 into the above tree