A study was conducted to determine if the salaries of librarians from two neighboring cities were equal. A sample of 15 librarians from each city was randomly selected. The mean from the first city was​ $28,900 with a standard deviation of​ $2300. The mean from the second city was​ $30,300 with a standard deviation of​ $2100. Construct a​ 95% confidence interval for mu 1minusmu 2.