3. A binary search tree (or BST) is a binary tree that has a special order property. That is For every node, Values of all the items in its left subtree are smaller than item in node X. Values of all the items in its right subtree are larger than the item in node X. Given the following trees, 1) specify whether each one is a binary tree or not and 2) whether each one is a binary search tree or not. If not, explain why? [3 points] 3.1 15 2 17 21