11. Define isEmpty member function of the binarySTADT class as declared on the page - 23. The function checks if the list is empty or not. If the list is empty, the function returns true else false. 12. Define countNodes member function of the binarySTADT class as declared on the page - 23. The function returns the number of nodes in the list. 13. Define preorder member function of the binarySTADT class as declared on the page 23. The function takes a tree node pointer as input parameter performs the preorder traversal of the tree/subtree with the given node as root. . Pre-condition the node pointer should not refer to the NULL