3. [10 points] Given a binary search tree T with a root node r, please write a recursive method N2C (r) that returns the number of internal nodes with two children in the tree. N2C(r)(r)//r is the root 1 if r==NIL 2. return 2. if r.left != NIL and r.right != NIL 3. return 4. else 5. return.