Expand the BST implementation we had in class, by implementing the following extra functions: 1) (20 points) write a function T next (TNode P) that returns the successor of the node that is pointed by P based on in-order traversal. 2) (20 points) Write a function void print_level (int level) that prints all the nodes at the input level. If the level does not exist, output a proper error message. 3) (30 points) write a function bool isBST(), which returns true if the current binary tree is a BST, and false otherwise. Note that: checking whether every node contains a value larger than its left child and smaller than its right child .... Does not work for all cases 4) (30 points) write a function T LCS(T& a, 15 T& b) that returns the smallest common ancestor of two nodes in a BST. If the tree is empty, or if it has less than three nodes, it 10 25 returns - 1. For example the LCS(6,12)= 10 12 20 30 18 22