A lot of people are in a exercise class, riding bikes.
The people are using exercise machines.
People use bikes as exercise machines.
exists e1 p1 x1 x2 x3.(for(p1,e1) & Theme(e1,x3) & Actor(e1,x1) & v_ride(e1) & n_bike(x3) & exists x4 x5.(in(x1,x4) & n_class(x4) & of(x4,x5) & n_exercise(x5)) & of(x1,x2) & n_people(x2) & n_lot(x1))
exists e1 x1 x2 x3.(n_people(x1) & Theme(e1,x2) & Actor(e1,x1) & v_use(e1) & n_machine(x2) & of(x2,x3) & n_exercise(x3))