Did M3 star a film editor that M1 and M2 employed
SELECT count(*) WHERE {
?x0 a ns:film.editor .
?x0 ns:people.person.employment_history/ns:business.employment_tenure.company M1 .
?x0 ns:people.person.employment_history/ns:business.employment_tenure.company M2 .
M3 ns:film.film.starring/ns:film.performance.actor ?x0
}