A senior manager, responsible for a group of 150 junior executives, is interested in the total amount of time per week spent by these people in internal meetings. A random sample of 36 of these executives was asked to keep diary records during the next week. When the results were analyzed, it was found that these sample members spent a total of 178 hours in internal meetings. The sample standard deviation was 4.6 hours. Find a 90% confidence interval for the total number of hours spent in internal meetings by all 150 junior executives in the week.