## A store 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)

A 5% discount indicates that her total purchase amount will be decreased by 5%. Paying full price could be shown as 1.00, so we must subtract 0.05 from the full price to represent the discounted total (1.00-0.05 = 0.95).Only one choice, D, contains this multiplier so we can be certain of this answer.