Mrs. Kelley asked her students to plot the number of books they read over the summer. A dot blot titled Books Read Over the Summer goes from 0 to 7. 0 has 1 dot, 1 has 3 dots, 2 has 6 dots, 3 has 2 dots, 4 has 3 dots, 5 has 1 dot, 6 has 2 dots, and 7 has 0 dots.

Using the dot plot, how many students answered the question?
3
6
17
18