A college statistics professor has office hours from 9am to 10:30am daily. A sample of waiting time to see professor(in minutes) is 10,12 20, 15, 17, 10, 30, 28,35, 28, 19, 27, 25, 22, 33, 37, 14, 21, 20, 23. Supposing standard deviation is 7.84, determine the 95.44% confidence interval for the population mean.
a) -7.7 to 7.8 minutes
b) 19.5 to 35.1 minutes
c) -3.5 to 3.5 minutes
d) 18.8 to 25.8 minutes