Who was a film producer that executive produced M2 and executive produced M3 and M4
SELECT DISTINCT ?x0 WHERE {
?x0 a ns:film.producer .
?x0 a ns:people.person .
?x0 ns:film.producer.films_executive_produced M2 .
?x0 ns:film.producer.films_executive_produced M3 .
?x0 ns:film.producer.films_executive_produced M4
}