For a 4-unit class like Statistics, students should spend average of 12 hours studying for the class. A survey was done on 21 students, and the distribution of total study hours per week is bell-shaped with a mean of 12 hours and a standard deviation of 2.7 hours.

Use the Empirical Rule to answer the following questions.

a) 68% of the students spend between __________ hours and_________hours on Statistics each week.

b) 95% of the students spend between_________hours and ________hours on Statistics each week.

c) 99.7% of the students spend between________hours and________hours on Statistics each week.