The safe fluoride-to-water ratio is 0.2 to 2.8 parts per million (ppm) gallons. What is the range in parts of fluoride that could be added to 250,000 gallons of water?

Monthly water bills for a city have a mean of $108.43 and a standard deviation of $36.98. find the probability that a randomly selected bill will have an amount greater than $173, which the city believes might indicate that someone is wasting water. would a bill that size be considered unusual?