2. A binary tree is a tree with 0, 1, or 2 child nodes. Let By denote the number of binary trees possible with n nodes. Therefore, Bi = 1 and B2 = 2. (a) Determine B3 and B, by drawing all possible binary trees in each case. (b) Generalize and define a recurrence relation for Br. As a hint, consider how many nodes there are in the left subtree and therefore how many nodes there are in the right subtree. (c) Solve the recurrence relation and show using Big O() notation