7.82 Suppose the manager of Croquettenbar Smaeck, a restaurant in Antwerp, Belgium, is estimating the queuing time of the customers until they receive their meals during peak hours. From a random sample of 18 customers, the average queuing time is 15 minutes with a standard deviation of 3.5 minutes. Assuming that the queuing time is normally distributed, determine a 95% confidence interval for the average queuing time during peak hours of all customers of Croquettenbar Smaeck.