We use the t distribution to construct a confidence interval for the population mean when the underlying population standard deviation is not known. Under the assumption that the population is normally distributed, find t_/2,df for the following scenarios. (You may find it useful to reference the t table. Round your answers to 3 decimal places.)

		t/2,df
a.	A 95% confidence level and a sample of 26 observations.
b.	A 99% confidence level and a sample of 26 observations.
c.	A 95% confidence level and a sample of 18 observations.
d.	A 99% confidence level and a sample of 18 observations.