Q331. Studying for an exam could raise a student's grade by a whole letter grade. But it turns out to not be a sure thing. Suppose research has shown that six hours of studying has a 60% chance of increasing your grade by one letter grade, a 25% chance of having no effect, and a 15% chance of actually lowering it by one letter grade (perhaps due to increased anxiety and not enough sleep).
Calculate the expected value of the investment of 6 hours of study time in terms of "letter grades per hour."