Your local bakery charges $6.00 for one dozen of doughnuts. (One dozen is 12 doughnuts). If you purchase any number of doughnuts over one dozen, you will only have to pay $0.40 per doughnut. The total cost of any number of doughnuts is given by the expression below.

6+.40(d−12)

Which part of the expression represents the number of doughnuts purchased at the discounted rate?


A. d


B. (d−12)

C. 6


D. .40(d−12)