Astore sells 12-packs of ballpoint pens for $1.09 each and composition books for $2.79 each. cindy buys m packs of ballpoint pens and n composition books. the store offers a 5% discount for every 50th customer who makes a purchase. if cindy gets the 5% discount, which expression will represent cindy’s bill?

a. 0.05 − 1.09m + 2.79n
b. 1.05 + 1.09m + 2.79n
c. 1.05(1.09m + 2.79n)
d. 0.95(1.09m + 2.79n)