Express Courier Service has found that the delivery time for packages is normally distributed, with mean 14 hours and standard deviation 3 hours.
(a) For a package selected at random, what is the probability
that it will be delivered in 18 hours or less? (Round your answer
to four decimal places.)
(b) What should be the guaranteed delivery time on all packages in
order to be 95% sure that the package will be delivered before this
time? (Hint: Note that 5% of the packages will be
delivered at a time beyond the guaranteed time period.) (Round your
answer to one decimal place.)
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