State the total degrees of freedom for the following t-tests. (if you need to use [infinity], enter infinity.)
(a) n = 21 for a one-independent sample t-test
(b) df1 = 13, n2 = 22 for a two-independent sample t-test
(c) critical value = 63.657 for a two-tailed test, α = 0.01
(d) critical value = 1.645 for a one-tailed test, α = 0.05