A researcher employed a new drug to treat 100 subjects with high cholesterol. For the patients in study, after two months of treatment the average decrease in cholesterol level was 80 milligrams per deciliter (mg/dl). suppose that the reduce in cholesterol after two months of taking the drug follows Normal distribution, with unknown mean \mu and standard deviation \sigma = 20 mg/dl. The researcher will develop a 90% confidence interval to estimate \mu.
Determine the researcher's 90% confidence interval for \mu ?______ mg/dl to ______mg/dl.