Were M2 and M3 executive produced by a person and executive produced by a art director
SELECT count(*) WHERE {
?x0 a ns:film.film_art_director .
?x1 a ns:people.person .
M2 ns:film.film.executive_produced_by ?x0 .
M2 ns:film.film.executive_produced_by ?x1 .
M3 ns:film.film.executive_produced_by ?x0 .
M3 ns:film.film.executive_produced_by ?x1
}