What is the average land area with a density of 815.48, and a Population larger than 411?
CREATE TABLE "references" (
  "urban_area_locality" text,
  "population" real,
  "land_area_hectares" real,
  "density_inh_km" real,
  "code" real
);
SELECT AVG("land_area_hectares") FROM "references" WHERE "density_inh_km"=815.48 AND "population">411;