Question: Which producer of the film 21 has played Lex Luthor?
Answer(s):
answer: Kevin Spacey

SPARQL query:
PREFIX ns: <http://rdf.freebase.com/ns/>
SELECT DISTINCT ?x
WHERE {
FILTER (?x != ns:m.04q78)
FILTER (!isLiteral(?x) OR lang(?x) = '' OR langMatches(lang(?x), 'en'))
ns:m.04q78 ns:film.film_character.portrayed_in_films ?y .
?y ns:film.performance.actor ?x .
?x ns:film.producer.film ns:m.02qczf7 . 
}