The man is on a black and white bike.
The man is on a bike.
A man is on a bike.
exists p1 x1.(n_man(x1) & exists s1 s2 x2.(on(x1,x2) & n_bike(x2) & a_white(s2) & Theme(s2,x2) & a_black(s1) & Theme(s1,x2)))
exists p1 x1.(n_man(x1) & exists x2.(on(x1,x2) & n_bike(x2)))