Scores on a marketing exam are known to be normally distributed with mean and standard deviation of 60 and 20.
a) Find the probability that a randomly selected student scores between 50 and 80.
b) Find the probability that a randomly selected student scores between 20 and 40.
c) The syllabus suggests that the top 15% of the students will get an A in the course. What is the minimum score required to get an A?