Four road workers planting a tree.
Four men are all friends
Friends aren't necessarily workers that plant a tree.
exists e1 x1 x2 x3.(Theme(e1,x3) & Actor(e1,x1) & v_plant(e1) & n_tree(x3) & n_worker(x1) & of(x1,x2) & n_road(x2) & card_eq_4(x1))
exists p1 x1.(all x2.(n_friend(x2) -> (x1 = x2)) & n_man(x1) & card_eq_4(x1))