A plumbing company has found that the length of time, in minutes, for installing a bathtub is normally distributed. The owner of the company hires a statistician to estimate the average length of time for installing a bathtub by his company. The statistician randomly selects a sample of 10 bathtub installations. The sample yielded = 150 minutes and s = 30 minutes. Construct a 95% confidence interval for the average length of time for installing a bathtub by the company.