Four people are singing Karaoke.
Some people are singing.
people are singing is same as people are singing
exists e1 x1 x2.(ne_nam_karaoke(x2) & Theme(e1,x2) & Actor(e1,x1) & v_sing(e1) & n_people(x1) & card_eq_4(x1))
exists e1 x1.(Actor(e1,x1) & v_sing(e1) & n_people(x1))