The water works commission needs to know the mean household usage of water by the residents of a small town in gallons p

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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 0.15
gallons. A previous study found that for an average family the
variance is 3.61 gallons and the mean is 19.4 gallons per day. If
they are using a 95% 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.