The time needed to complete the final examination in particular college course is normally distributed with mean of 80 minutes and standard deviation of 10 times. Answer the following problems.
a. Find out the probability of completing the exam in one hour or less?
b. Find out the probability that a student will complete the exam in more than 60 minutes but less than 75 minutes?
c. Suppose that the class has 60 students and that the examination period is 90 minutes in length. How many students do you expect will be unable to complete the exam in allotted time?