Students in 11th and 12th grades were surveyed to choose a favorite free-time activity: playing computer games, listening to music, or watching movies/TV.


Leisure Time Activity Preferences
Computer Games Music Watching movies/TV Row totals
11th grade students 4 20 16
12th grade students 15 13 40
Column totals 32 29 80


What is the marginal frequency of students who prefer playing computer games?