In the past, every ten-percentage-point increase in cigarette prices in the country of Coponia has decreased per capita sales of cigarettes by four percent. Coponia is about to raise taxes on cigarettes by 9 cents per pack. The average price of cigarettes in Coponia is and has been for more than a year 90 cents per pack. So the tax hike stands an excellent chance of reducing per capita sales of cigarettes by four percent.

Which of the following is an assumption on which the argument depends?

【选项】At present, the price of a pack of cigarettes in Coponia includes taxes that amount to less than ten percent of the total selling price.