2 {(1,a); (1,b); (1,c)} 3 {(1,a); (2,c)} 4 {(3,b); (3,c); (4,c)} 5 {(2,c); (3,c); (4,b); (4,c)} 6 {(4,a); (4,b); (4,c)} 7 {(2,b)}