Ahypothesis will be used to test that a population mean equals 7 against the alternative that the population mean does not equal 7 with unknown variance. what are the critical values for the test statistic t0 for the following significance levels and sample sizes?

(a) ? = 0.01 and n = 20 (b) ? = 0.05 and n = 12 (c) ? = 0.10 and n = 15