Finding the Mode of Study Hours

In a recent survey, 100 students were asked how many hours they study each week. The following data was recorded for the number of hours studied:

0, 2, 2, 3, 4, 4, 4, 5, 5, 6, 6, 6, 6, 7, 8, 10, 12, 12, 12, 13, 15

Based on this data, what is the mode of the number of hours studied by the students?