To boost holiday sales, a jewelry store in Bismarck, North Dakota, is advertising the following promotion: "If more than eight inches of cumulative snow fall on December 24, 25, 26, 27, and 28, you get your money back on all purchase made on December 17." To analyze this promotion, the store manager has collected data and determined that snowfall over this 5-day period in December is normally distributed with an average of 6.7 inches and standard deviation of 0.579 inches. What is the probability that the store will have to refund the money to its December 17 customers? If required, round your answer to four decimal places.