The library case study described in Exercise 12.14 is extended to include the fact that the library has a significant stock of books that are no longer suitable for loaning out. These books can be sold for a fraction of the original cost. However, not all library books are eventually sold as many are considered too damaged to sell on, or are simply lost or stolen. Each book copy that is suitable for selling has a price and the date that the book is no longer to be loaned out. Introduce enhanced concepts into the ER model shown in Figure 13.12 and described in Exercise 12.14 to accommodate this extension to the original case study.