A large airline wants to estimate its average number of unoccupied seats per flight over the past year. To accomplish this, the records of 30 flights are randomly selected and the number of unoccupied seats is noted for each of the sampled flights. The data is tabulated below.
8 18 13 11 22 14
9 18 10 18 13 15
7 16 11 10 20 19
13 16 19 18 22 23
6 15 11 12 18 12
Give a 90% confidence interval for the average number of empty seats. Use the sample standard deviation rounded to 3 decimal places. Put your answers in (a, b) form with parentheses and space after the comma required. Round your answers to two decimal places!