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Determine the t-value in each of the cases. Click the icon to view the table of areas under the t-distribution. (a) Find the t-value such that the area in the right tail is 0.20 with 28 degrees of freedom. (Round to three decimal places as needed.) (b) Find the t-value such that the area in the right tail is 0.25 with 22 degrees of freedom. (Round to three decimal places as needed.) (c) Find the t-value such that the area left of the t-value is 0.005 with 15 degrees of freedom. [Hint: Use symmetry.] (Round to three decimal places as needed.) (d) Find the critical t-value that corresponds to 80% confidence. Assume 22 degrees of freedom. (Round to three decimal places as needed.)