Which situation is not an example of a linear function?
A) The distance traveled if a car is driving at a constant rate of 60 miles per hour.
B) The cost of the bill if a cell phone company charges an initial fee of $25 plus $45 per month.
C) The amount of cake each person gets to eat if a cake is divided equally among the guests at a party.
D) The amount of time spent grading papers if a teacher grades one paper every 8 minutes and takes a 10 minute break.