Preconditions: Number of copies must be positive, but not more than MAX_COPIES
One, but not both, of authorFirst and authorLast may be null
Postcondition: The book is added to the library and the number of books in the library is incremented
Preconditions: none
Postcondition: The patron is added to the list of patrons, the number of patrons in the library is incremented
and a library card number is assigned.