The US Department of Transportation provides the number of miles that the residents of the 75 largest metropolitan areas travel per day in a car. Suppose that for a random sample of 50 Buffalo residence the mean is 22.5 miles a day and the standard deviation is 8.4 Miles a day, and for an independent random sample of 40 Boston residents the main is 18.6 miles a day and the standard deviation is 7.4 miles a day. a. What is the point estimate of the difference between the main number of miles that Buffalo residence travel per day in the mean number of miles that Boston residents travel per day? b. What is the 95% confidence interval for the difference between the two population means?