For a 4-units class like Statistics, students should spend average of 12 hours studying for the class. A survey was done on students, and the distribution of total study hours per week is bell-shaped with a mean of 14 hours and a standard deviation of 3 hours. Use the Empirical Rule to answer the following questions. a) 68% of the students have study hours that are between and c) What percentage of the students have study hours that are below 20? %