b) The length of time taken by a statistics professor to solve The Globe & Mail cryptic crossword has a normal distribution. It is known that the probability of needing more than 20 minutes is 0.5, while the probability of needing more than 30 minutes is 0.1587. (i) Find the mean and the standard deviation of the professor's solving time.

Mean= SD =

e) From the survey we find that the Commerce 290 Grade (call this variable, X) has a symmetric, bell-shaped distribution. Also, 95% of the grades fall in the range 53 to 93 Use that information to compute the mean and standard deviation of X. Report to at most one decimal place.

Mean of X= SD of X=