What is the total population with a population density less than 29,384.8 in San Nicolas?
CREATE TABLE "administrative_districts" (
  "district" text,
  "s_barangay" real,
  "population_2010_census" real,
  "area_has" real,
  "pop_density_per_km2" real
);
SELECT SUM("population_2010_census") FROM "administrative_districts" WHERE "pop_density_per_km2"<'29,384.8' AND "district"='san nicolas';