A boy is covered with marker.
The boy is clean.
If one is covered with marker, they cannot also be considered clean.
exists e1 x1 x2.(with(e1,x2) & n_marker(x2) & Theme(e1,x1) & v_cover(e1) & n_boy(x1))
exists s1 x1.(n_boy(x1) & Theme(s1,x1) & a_clean(s1))