Given that:
- The sample size is 28 city residents:

- The mean of the time (in years) they had lived at their present address was:

- The standard deviation (in years) of the population was:

Then, you need to use the following formula for calculating the Confidence Interval given the Mean:

Where μ is the sample mean, σ is the standard deviation, "z" is the z-score, and "n" is the sample size.
By definition, the z-score for a 90% confidence interval is:

Therefore, you can substitute values into the formula and evaluate:

You get that the lowest value is:

And the highest value is:

Hence, the answer is:
