Construct a 99 percent confidence interval for the midsize model's mean mileage for 50 cars. Before the automaker selected the population of 50 mileages, it randomly selected the following sample of five mileages: 30.7,31.9,30.3,32.0, and 31.6 . This sample has mean x=31.3. Assuming that the population of all mileages is normally distributed and that population standard deviation is known to equal .98