A row of bikers wearing red and black.
People are on bikes.
Bikers are people who are on bikes.
exists e1 s1 s2 x1 x2 x3.(a_topic(x1) & of(x1,x2) & for(e1,s2) & Theme(s2,x3) & a_black(s2) & for(e1,s1) & Theme(s1,x3) & a_red(s1) & Actor(e1,x3) & v_wear(e1) & (x2 = x3) & n_biker(x2) & n_row(x1))
exists p1 x1.(exists x2.(on(x1,x2) & n_bike(x2)) & n_people(x1))