b. Silver Star, Inc., has a number of stores in major metropolitan shopping centers. The company's sales experience indicates that daily cell phone sales in its stores follow a normal distribution with a mean of 60 and a standard deviation of 15. The marketing department conducts a number of routine analyses of sales data to monitor sales performance. What proportion of store sales days will have sales between 85 and 95 given that sales are following the historical experience? (answer in three decimal places)