Ruth 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 ruth paid for the book when she returned it x days after the due date:

2 + 0.25x

what does the second term of the expression represent?

the total late fee paid

the fixed rental for the book

the late fee per day for the book

the number of days the book was overdue