A Biology professor is teaching sections A and B of BIOL 1000. The professor knows from the past that the student exam marks of section A follows a normal distribution with an average of 65, and a standard deviation of 10 while the student's exam marks of section B follows a normal distribution with an average of 70, and a standard deviation of 20. a) Find the probability that the average exam marks by a random sample of 100 students in section B is less than 67. b) What is the probability that the average exam marks of 81 randomly selected students from section A is one mark higher than the average exam marks of 100 randomly selected students from section B? c) The professor declares that no more than one-quarter of section B's students will get average marks. What is the probability that in a random sample of the 80 section B students, more than 28 will get the average marks? d) (Solve this part independently). A random sample of 6 National bank employees was taken to help estimate the average amount of time(x) employees spent per week on their cell phones. The sample data and some relevant information are listed below: 13, 5, 6, 10,7, 12. Ex = 53, Sample Variance of x = 10.9667 Find an unbiased estimator of the average time per week for all bank employees