Replacement times for TV sets are normally distributed with a mean of 8.2 years and a standard deviation of 1.1 years (based on data from "Getting Things Fixed," Consumer Reports).
a. Find the replacement time that separates the top 20% from the bottom 80%.
b. Find the probability that a randomly selected TV will have a replacement time of less than 5.0 years.
c. If you want to provide a warranty so that only 1% of the TV sets will be replaced before the warranty expires, what length of time would you recommend for the warranty?