Construct AVL trees by inserting the elements successively, starting with the empty tree. a) 1, 2, 3, 4, 5, 6 b) 6, 5, 4, 3, 2, 1 c) 3, 6, 5, 1, 2, 4 (Note: Observe the final trees and you will find that although all of them have the same data, the tree are not necessarily the same.)