A saxophonist and singer perform.
Two people are performing.
The are performing because they perform.
exists e1 x1 x2 x3.(Actor(e1,x1) & v_perform(e1) & n_singer(x3) & n_saxophonist(x2) & subset_of(x3,x1) & subset_of(x2,x1))
exists e1 x1.(Actor(e1,x1) & v_perform(e1) & n_people(x1) & card_eq_2(x1))