question: Did M1 , M2 , and M3 employ a film 's art director
query: SELECT count(*) WHERE {
  ?x0 ns:film.film_art_director.films_art_directed ?x1 .
  ?x1 a ns:film.film .
  M1 ns:business.employer.employees/ns:business.employment_tenure.person ?x0 .
  M2 ns:business.employer.employees/ns:business.employment_tenure.person ?x0 .
  M3 ns:business.employer.employees/ns:business.employment_tenure.person ?x0
  }