(a) Determine the critical value for a right-tailed test of a population standard deviation with 16 degrees of freedom at the a = 0.01 level of significance.

(b) Determine the critical value for a left-tailed test of a population standard deviation for a sample of size n = 14 at the a = 0.01 level of significance.

(c) Determine the critical values for a two-tailed test of a population standard deviation for a sample of size n = 61 at the a = 0.05 level of significance.