A city planner wants to estimate the average monthly residential water usage in the city. He selected a random sample of 42 households from the city, which gave the mean water usage to be 3409.30 gallons over a one-month period. Based on earlier data, the population standard deviation of the monthly residential water usage in this city is 387.90 gallons. Make a 97% confidence interval for the average monthly residential water usage for all households in this city.

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