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Determine the t-value in each of the cases, (a) Find the t-value such that the area in the right tail is 0.05 with 18 degrees of freedom. (Round to three decimal places as needed.) (b) Find the t-value such that the area in the right tail is 0.10 with 30 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 7 degrees of freedom. (Hint: Use symmetry.) (Round to three decimal places as needed.) (d) Find the t-value that corresponds to building a 95% confidence interval. Assume 23 degrees of freedom. (Round to three decimal places as needed.)