The salaries for 25 UF employees were recorded and the data…

The salaries for 25 UF employees were recorded and the data appears to be approximately normally distributed.  The sample mean was $64,500 and a population standard deviation was known to be $4,500 and used to construct a 95% confidence interval on the population mean salary.  For this confidence interval from which distribution should the critical value be taken from to produce its lower and upper limits?