2. An airline company wants to estimate the mean number of unoccupied seats per flight over the past year. To accomplish this investigation, the records of 400 flights are randomly selected from the files, and the number of unoccupied seats is counted for each flight. The sample mean and standard deviation are 7.4 seats and 5.2 seats, respectively. Estimate the mean number of unoccupied seats per flight over the past year (population mean u) at 98% confidence level