Consider the following enterprise, which includes books, authors and publishers. Authors are people with normal attributes, like name, date of birth, etc., but in addition they wrote one or more books. A book has the usual attributes, such as title, ISBN, publication date, etc. Publishers are companies that publish books. They have an address, phone numbers (typically more than one), name, etc. A book can be written by more than one author, but it can be published by only one publisher. Books do not write themselves and do not publish themselves (hint: these are constraints). An author can write more than one book and to be called an author one, of course, has to write at least one book. Represent the above as an E-R diagram: include all relevant constraints.