Final averages are typically approximately normally distributed with a mean of 70 and a standard deviation of 10.5. Your professor says that the top 9% of the class will receive an A; the next 20%, a B; the next 40%, a C; the next 21%, a D; and the bottom 10%, an F. (Give your answers correct to one decimal place.)
(a) What average must you exceed to obtain an A?
(b) What average must you exceed to receive a grade of C or better?
(c) What average must you obtain to pass the course? (You'll need a D or better.)