Carbon monoxide (CO) emissions for a certain kind of car vary with mean 2.881 g/mi and standard deviation 0.6 g/mi. A company has 60 of these cars in its fleet. Let y overbar represent the mean CO level for the company's fleet. a) What's the approximate model for the distribution of y overbar? Explain. b) Estimate the probability that y overbar is between 3 and 3.2 g/mi. c) There is only a 10% chance that the fleet's mean CO level is greater than what value?