What is the center of the data in the dot plot?

Number of Minutes to Finish the Quiz
A dot plot going from 10 to 15. 10 has 4 dots, 11 has 3 dots, 12 has 7 dots, 13 has 6 dots, 14 has 3 dots, and 15 has 6 dots.
12
12.5
13
13.5