please help me problem4 , also if you can work on extra point is best

Problem 4: A binary tree is full if all vertices have either 0 or two children Let Bn denote the number of full binary trees with n vertices 1. What are the values of B3, B5, and B7? 2. For general n, derive a recurrence relation for Bn. Include base cases Extra Credit (5 points): Suppose you are starting an exercise routine Each day, you can either lift weights, jog, or rest. The only rule is that you cannot lift weights for two days in a row. Write a recurrence relation describing how many sequences of exercises can you follow over a course of N days