One college class had a total of 70 students. The average score for the class on the last exam was 83.8 with a standard deviation of 4.5. A random sample of 31 students was selected a. Calculate the standard error of the mean. b. What is the probability that the sample mean will be less than 857 c. What is the probability that the sample mean will be more than 847 d. What is the probability that the sample mean will be between 82.5 and 84.57 a. The standard error of the mean is (Round to two decimal places as needed.)