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