Suppose Scarlett decides to borrow the book from the library. Which result would be a cost?

 - Scarlett will give up the chance to keep the book as long as she wants.
 - Scarlett will save some money by not buying the book.
This result is a cost. It involves giving up or spending something that Scarlett wants or needs:
Scarlett will give up the chance to keep the book as long as she wants.