Because of different sales ability, experience, and devotion, the incomes of real estate agents vary considerably. Suppose that in a large city the annual income is normally distributed with a standard deviation of $15,000. A random sample of 16 real estate agents was asked to report their annual income (in $1,000). The responses are listed here. Determine the 99% confidence interval estimate of the mean annual income of all real estate agents in the city.

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