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The water works commission needs to know the mean household usage of water by the residents of a small town in gallons per day. They would like the estimate to have a maximum error of 0.11
gallons. A previous study found that for an average family the standard deviation is 2.3
gallons and the mean is 19.9
gallons per day. If they are using a 80%
level of confidence, how large of a sample is required to estimate the mean usage of water? Round your answer up to the next integer.