Refer to the accompanying data display that results from a sample of airport data speeds in Mbps. Complete parts​ (a) through​ (c) below. TInterval ​(13.046,22.15) x overbarequals17.598 Sxequals16.01712719 nequals50 a. Express the confidence interval in the format that uses the​ "less than" symbol. Given that the original listed data use one decimal​ place, round the confidence interval limits accordingly. nothing Mbpsless thanmuless than nothing Mbps ​(Round to two decimal places as​ needed.) b. Identify the best point estimate of mu and the margin of error. The point estimate of mu is nothing Mbps. ​(Round to two decimal places as​ needed.) The margin of error is Eequals nothing Mbps. ​(Round to two decimal places as​ needed.) c. In constructing the confidence interval estimate of mu​, why is it not necessary to confirm that the sample data appear to be from a population with a normal​ distribution? A. Because the sample size of 50 is greater than​ 30, the distribution of sample means can be treated as a normal distribution. B. Because the sample standard deviation is​ known, the normal distribution can be used to construct the confidence interval. C. Because the population standard deviation is​ known, the normal distribution can be used to construct the confidence interval. D. Because the sample is a random​ sample, the distribution of sample means can be treated as a normal distribution.