There is concern about the speed of automobiles traveling over a particular stretch of highway. For a random sample of 28 automobiles, radar indicated the following speeds in miles per hour. 58 63 68 57 55 72 58 69 53 55 60 66 51 59 53 64 58 57 66 61 65 70 64 65 57 56 61 59 a. Check for evidence of nonnormality. b. Find a point estimate of the population mean that is unbiased and efficient. c. Use an unbiased estimation procedure to find a point estimate of the variance of the sample mean. a. Is there evidence of nonnormality? O A. Yes, because the normal probability plot of the data deviates from a straight line. B. No, because the normal probability plot of the data is reasonably close to a straight line. O C. Yes, because the normal probability plot of the data is reasonably close to a straight line. O D. No, because the normal probability plot of the data deviates from a straight line. b. An unbiased and efficient point estimate of the population mean is 60.71 . (Round to two decimal places as needed.) c. A point estimate of the variance of the sample mean is (Round to two decimal places as needed.)