1. (9 points) An economist is interested in the average cost of gasoline in a metropolitan area. She records the price of regular unleaded gas at 15 stations and finds a mean of $4.50/gallon with a standard deviation of $0.25/gallon. Please calculate: a. (3 points) The 90% confidence interval on the average price of regular unleaded gas b. (3 points) The 95% confidence interval c. (3 points) The 99% confidence interval