Your friend has $80 when he goes to the fair. He spends $4 to enter the fair and $12 on food. Rides at the fair cost $1.25 per ride. Which function can be used to determine how much money he has left over after x rides?

A) f(x) = 1.25x + 64

B) f(x) = -16x + $80

C) f(x) = -1.25x + 64

D) f(x) = -1.25x - 64