4. The distribution of exam grades for an introductory Statistics class is negatively skewed with a mean of u = 71.5 and a standard deviation of o = 12. [10 Marks] a. For a sample of n = 9 students, what is the probability that the average grade is greater than 75? [2 marks] b. For a sample of n = 36 students, what is the probability that the average grade is greater than 75? [4 Marks] c. For a sample of n = 36 students, what is the probability that the average grade is between 70 and 75? [4 Marks]