The following box plot shows the number of years during which 40 schools have participated in an interschool swimming meet:

a box and whisker plot is drawn using a number line from 0 to 10 with primary markings and labels at 0, 5, 10. in between two primary markings are 4 secondary markings. the box extends from 1 to 6 on the number line. there is a vertical line at 3.5. the whiskers end at 0 and 8. above the plot is written duration of participation. below the plot is written years.

at least how many schools have participated for more than 1 year and less than 6 years?

4 schools
8 schools
10 schools
20 schools