A group of \( 40 \) students appeared in an examination of \( 3 \) subjects – Mathematics, Physics and Chemistry. It was found that all students passed in at least one of the subjects, \( 20 \) students passed in Mathematics, \( 25 \) students passed in Physics, \( 16 \) students passed in Chemistry, at most \( 11 \) students passed in both Mathematics and Physics, at most \( 15 \) students passed in both Physics and Chemistry, at most \( 15 \) students passed in both Mathematics and Chemistry. The maximum number of students passed in all the three subjects is \( \_\_\_\_\_ \).
