EXERCISE 9: BINARY SEARCH TREE a. b. C. Write a function that counts the number of items in a binary tree. Write a function that returns the sum of all the keys in a binary tree. Write a function that returns the maximum value of all the keys in a binary tree. Assume all values are nonnegative; return -1 if the tree is empty. Write C++ function that prints all the keys less than a given value, v, in a binary tree. d