Produce a Diagram 0 data flow diagram for the following case study:
Mary Jones owns a second hand book store called Classic Cover in Washington DC. Besides buying and selling second hand classic books, Mary has a small library of books now out of publication which she loans out. Before anyone can borrow any books, however, they must register to join the library club and pay a deposit. The deposit is returned when a person stops being a member and if all the borrowed books have been returned.
When someone wants to sell a book, Mary searches her database of books to see if she already has a copy either in the library or for sale. If so, she checks how much she paid for the book or copies she already has. If she already has several copies of the book, she will not buy the book. If she doesn't have a copy of the book, she will offer to buy it.