Each of the 59 members in a high school class is required to sign up for a minimum of one
and a maximum of three academic clubs. The three clubs to choose from are the poetry
club, the history club and the writing club. A total of 22 students sign up for the poetry
club, 27 students for the history club and 28 students for the writing club. If 6 students
sign up for exactly two clubs, how many students sign up for all three clubs?