One gallon of gas is put into each of 30 test cars. The resulting gas-mileage values of the sample are computed with mean of 28.5 gallons per mile and a standard deviation of 1.2 miles per gallon. What is the 95% confidence interval estimate of the mean mileage? O (27.36, 29.64) (28.42, 28.58) O (28.46, 28.54) O (28.1, 28.9) O (27.3, 29.7)