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.