dontrelle checked out 4 library books, which have now been overdue for 12 days. His total fine so far is $9.60 . which of these equations can be used to determine the amount the library charges as a fine per day per overdue book?

A. 4f=$9.60/4

B. 4f=$9.60

C. 12f=$9.60/4

D. 12f=$9.60