Which Subregion has a No P. of 4, and a Pop/Area (1/km²) of 534?
CREATE TABLE "municipalities" (
  "name" text,
  "area_km" real,
  "pop" real,
  "pop_area_1_km" real,
  "no_p" real,
  "no_c_no_t" text,
  "subregion" text
);
SELECT "subregion" FROM "municipalities" WHERE "no_p"=4 AND "pop_area_1_km"=534;