The weekly salaries of teachers in one state are normally distributed with a mean of $490 and a standard deviation of $45. what is the probability that a randomly selected teacher earns more than $525 a week?

Do one of the following, as appropriate: (a) find the critical value z subscript alpha divided by 2 , (b) find the critical value t subscript alpha divided by 2 . 99%; nequals 17; sigma is unknown; population appears to be normally distributed.