Bob Nale is the owner of Nale's Texaco GasTown. Bob would like to estimate the mean number of litres (L) of gasoline sold to his customers. Assume the number of litres sold follows the normal distribution with a standard deviation of 34 L. From his records, he selects a random sample of 26 sales and finds the mean number of litres sold is 80. Develop a 90% confidence Interval for the population mean.