Many passengers on cruise ships wear skin patches that supply Dramamine to the body for the purpose of preventing motion sickness. A claim about the mean dosage amount is tested with a significance level of alpha = 0.05. The conditions are such that the standard normal distribution can be used (because the central limit theorem applies). Find the critical value(s) of z if the test is (a) two-tailed, (b) left-tailed, and (c) right-tailed.