Aflight instructor charges $50 per lesson, plus an
additional fee for the use of his plane. the charge for
the use of the plane varies directly with the square root
of the time the plane is used. if a lesson plus 16 minutes
of plane usage costs $90, what is the total amount
charged for a lesson having 36 minutes of plane usage?

An automobile assembly line operation has a scheduled mean completion time, μ, of 12 minutes. the standard deviation of completion times is 1.6 minutes. it is claimed that, under new management, the mean completion time has decreased. to test this claim, a random sample of 33 completion times under new management was taken. the sample had a mean of 11.2 minutes. assume that the population is normally distributed. can we support, at the 0.05 level of significance, the claim that the mean completion time has decreased under new management? assume that the standard deviation of completion times has not changed.