Kylie borrowed a book from a library. The library charged a fixed rental for the book and a late fee for every day the book was overdue. The expression below shows the charges Kylie paid for the book when she returned it x days after the due date: 2 + 0.25x

What does the constant term of the expression represent?

The late fee for the book
The fixed rental for the book
The number of books borrowed
The number of days the book was overdue