Children are pulling on a rope.
The children are in class.
If one is in class one is not pulling on a rope simultaneously.
exists e1 x1 x2.(on(e1,x2) & n_rope(x2) & Actor(e1,x1) & v_pull(e1) & n_child(x1))
exists p1 x1.(n_child(x1) & exists x2.(in(x1,x2) & n_class(x2)))