The gas mileage for a certain model of car is known to have a standard deviation of 6 mi/gallon. A simple random sample of 49 cars of this model is chosen and found to have a mean gas mileage of 28.4 mi/gallon. Construct a 97% confidence interval for the mean gas mileage for this car model. a) O [26.540, 30.260] b) O [26.788, 30.012] c) O [15.380, 41.420] d) O [17.114, 39.686] e) O [28.134, 28.666] None of the above