An agronomist examines the cellulose content of a variety of alfalfa hay. Suppose that the cellulose content in the population has standard deviation σ= 9 milligrams per gram (mg/g). A sample of 15 cuttings has mean cellulose content x = 145 mg/g.
(a) Give a 90% confidence interval for the mean cellulose content in the population. (Round your answers to two decimal places.)