The researcher wants to estimate the mean trough level (the lowest dosage of medication required to see clinical improvement of symptoms) for a medication used to treat arthritis and they conduct a study among 29 newly diagnosed arthritis patients and finds the mean trough to be 3.9 micrograms/mL with a standard deviation of 1.1 micrograms/mL. Accordingly, find the confidence interval for the mean trough level under 95% confidence level. Show your work to get full credits.