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 36 cars of this model is chosen and found to have a mean gas mileage of 28.4 mi/gallon. construct a 99% confidence interval for the mean gas mileage for this car model. a) (27.971, 28.829) b) (12.944, 43.856) c) (25.824, 30.976) d) (26.074, 30.726) e) (14.444, 42.356) f) none of the above