question: Were M2 , M3 , and M4 employed by a Mexican film producer 's country of nationality
query: SELECT count(*) WHERE {
  ?x0 ^ns:people.person.nationality ?x1 .
  ?x1 a ns:film.producer .
  ?x1 ns:people.person.nationality ns:m.0b90_r .
  M2 ns:people.person.employment_history/ns:business.employment_tenure.company ?x0 .
  M3 ns:people.person.employment_history/ns:business.employment_tenure.company ?x0 .
  M4 ns:people.person.employment_history/ns:business.employment_tenure.company ?x0
  }