Step 1 :The question is asking for the critical value and the rejection region for a right-tailed t-test with a level of significance of 0.10 and a sample size of 21.
Step 2 :The critical value is given as 1.325. This is the value beyond which we would reject the null hypothesis in a right-tailed test.
Step 3 :The rejection region for a right-tailed test is all values greater than the critical value.
Step 4 :So, the rejection region for this test is all values greater than 1.325.
Step 5 :\(\boxed{t>1.325}\)