Calculating the Median Study Hours

A researcher collected the following data on the number of hours spent studying per week by 20 students:

6, 10, 10, 12, 15, 20, 20, 25, 25, 30, 30, 35, 35, 35, 40, 40, 45, 50, 55, 60

Based on this data, determine the median number of hours studied per week.