plz help solve tree problem.... A tree is called a 3-1 tree if every vertex in the tress has degree equal to either 3 or 1. 1. Draw all 3-1 trees with four or fewer vertices of degree 3. 2. Prove that a 3-1 tree must have an even number of vertices. 3. Find a formula for the number of leaves in a 3-1 tree that has exactly m vertices.