Determine the t-value in each of the cases.

(a) Find the t-value such that the area in the right tail is 0.01 with 13 degrees of freedom.

(b) Find the t-value such that the area in the right tail is 0.05 with 21 degrees of freedom.

(c) Find the t-value such that the area left of the t-value is 0.02 with 19 degrees of freedom. [Hint: Use symmetry.] (

d) Find the critical t-value that corresponds to 99% confidence. Assume 11 degrees of freedom.