How many communes associated with over 10 cantons and an area (Square km) of 1,589?
CREATE TABLE "complete_list" (
  "dep" text,
  "chief_town" text,
  "arrondissement" text,
  "population_1999" text,
  "area_square_km" real,
  "pop_density" real,
  "cantons" real,
  "communes" real
);
SELECT AVG("communes") FROM "complete_list" WHERE "cantons">10 AND "area_square_km"='1,589';