Stock Prices for Abercrombie and Fitch Fell Steadily by an Average

Stock prices for Abercrombie and Fitch fell steadily by an average of $0.94 per day from a high of $83.67 per share on December 24, 2007 to $70.05 on January 15, 2008.Let $P_{1}$ be the price of a share of stock on December 24, 2007.Write a formula for $P_{n}$ , the price of a share on the $n^{\text {th }}$ day after December 24.