A cost accountant wished to establish the average amount spent by executives per day on travel and lodging. Then a comparison, between the average and the amount turned in to be reimbursed, will be made and unreasonably high or low expense amounts investigated. A random sample of 81 executive expense receipts is taken. The average in the sample was $105. The sample standard deviation is s = $15. Prepare a 99% confidence interval for the population mean. What are the positive and negative t-scores; that is, t and t?