A firefighter is working at a fire.
A firefighter is at home with the flu.
A firefighter cannot be work at a fire and at home with the flu simultaneously.
exists e1 x1 x2.(at(e1,x2) & n_fire(x2) & Actor(e1,x1) & v_work(e1) & n_firefighter(x1))
exists p1 x1 x3.(n_flu(x3) & exists x2.(at(x1,x2) & with(x2,x3) & n_home(x2)) & n_firefighter(x1))