An orchestra rehearses in a church.
There is nobody singing in the church.
if an orchestra is rehearsing at a church then there cannot be nobody singing in the church. it is occupied.
exists e1 x1 x2.(in(e1,x2) & n_church(x2) & Actor(e1,x1) & v_rehearse(e1) & n_orchestra(x1))
exists p1 x1 x4.(n_church(x4) & -exists e1 x2 x3.((x1 = x2) & in(e1,x4) & Actor(e1,x3) & v_sing(e1) & (x2 = x3) & n_person(x2)))