Please code in Java and ignore question 2, thank you!

1. Write a Java method that takes as its only input parameter a single integer, n, and returns the number of unique binary search trees that can be constructed with integers 1 through n. (Hint: You'll probably want to do this recursively.) (Note: This is not asking for the number of maximally tall BSTs. The BSTs can be any height.) 2. Work through the deletion exercises in 2-4-deletion-supplementary.pdf (attached above). Note: The PDF includes solutions 3. If we start off with an empty tree (null), what is the minimum number of insert and delete operations necessary to create the following 2-4 tree? (16) (12) (20) Sorry this diagram is not as fancy as the one below.)