Your final statistics averages are typically approximately normally distributed with a mean of 80 and standard deviation of 10. Professor Han says that the top 8% of the class will receive an A; the next 22%, a B; the next 40%, a C; the next 23%, a D; and the bottom 7%, a F. a). What average must you exceed to obtain an B or better? b). What average must you exceed to receive a grade C or better