First I would create a Book class, this class would have the Title, Author, and a boolean flag to indicate if it was checked out or not. Then I would create a Library class to keep track of the Books. I would use a List to store the Books. There would be several methods to interact with the Library and Books, such as AddBook (to add a Book to the List), some CheckIn and CheckOut methods that would handle the boolean flag, and a method to show what books are available. This answer was sufficient enough to pass to the next round.