A book consists of an author, title, and ISBN number (all of which can never change once the book is created). A library book is a book that also contains a due date and the current holder of the book, which is either a String representing a person who has checked the book out or null if the book is currently not checked out. Both the due date and holder of the book can change over time. A library contains library books and supports the following operations: 1. Add a library book to the library. 2. Check out a library book by specifying its ISBN number and new holder and the due date. 3. Determine the current holder of a library book given its ISBN number.

a. Write two interfaces: Book and LibraryBook that abstract the functionality described above.

b. Write a library class that includes the three methods specified. In implementing the Library class, you should maintain the library books in an ArrayList. You may assume that there are never any requests to add duplicate books.