question: Did M5 and M6 write a film whose prequel was executive produced by M1 , M2 , M3 , and M4
query: SELECT count(*) WHERE {
  ?x0 a ns:film.film .
  ?x0 ns:film.film.prequel ?x1 .
  ?x1 ns:film.film.executive_produced_by M1 .
  ?x1 ns:film.film.executive_produced_by M2 .
  ?x1 ns:film.film.executive_produced_by M3 .
  ?x1 ns:film.film.executive_produced_by M4 .
  M5 ns:film.writer.film ?x0 .
  M6 ns:film.writer.film ?x0
  }