Were M1 , M2 , and M3 employed by a production company
SELECT count(*) WHERE {
?x0 a ns:film.production_company .
M1 ns:people.person.employment_history/ns:business.employment_tenure.company ?x0 .
M2 ns:people.person.employment_history/ns:business.employment_tenure.company ?x0 .
M3 ns:people.person.employment_history/ns:business.employment_tenure.company ?x0
}