Past experience indicates that the time required for high school seniors to complete a standardized test is a normal random variable with a mean of 35 minutes. A random sample of 20 high school seniors took an average of 33. 1 minutes to complete this test with a standard deviation of 4. 3 minutes. Test the hypothesis verifying that, at the 0. 05 level of significance, that completion time is at least 35 minutes. What is the relevant limit of the critical region?.