Notre-Dame-De-Lourdes has what average area km 2?
CREATE TABLE "parishes" (
  "official_name" text,
  "status" text,
  "area_km_2" real,
  "population" real,
  "census_ranking" text
);
SELECT AVG("area_km_2") FROM "parishes" WHERE "official_name"='notre-dame-de-lourdes';