Tell me the average rank for dharma productions before 2013
CREATE TABLE "biggest_third_week_domestic_nett_gross_e" (
  "rank" real,
  "movie" text,
  "year" real,
  "studio_s" text,
  "third_week_nett_gross" real
);
SELECT AVG("rank") FROM "biggest_third_week_domestic_nett_gross_e" WHERE "studio_s"='dharma productions' AND "year"<2013;