Premise: cigarette tax went up by $0.08 and sales went down.
Conclusion: higher cigarette costs mean fewer sales
Assumption: No change in cigarette cost other than the $0.08 tax.
(D) tells us that the pre-sale cost of cigarettes did not change my more than $0.08 cheaper. Because if it had, then cigarette costs could be less than the year prior, even though the taxes went up. In an extremem scenario, last year, cigarettes cost $10 per pack, and this year, they cost $1.08. Even though I added $0.08 tax, I could still discount my product so that it is cheaper than it was before.
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Joe Lucero
Manhattan GMAT Instructor