What is the Hanyu Pinyin with an area of 400?
CREATE TABLE "subdivisions" (
  "name" text,
  "hanzi" text,
  "hanyu_pinyin" text,
  "uyghur_uey" text,
  "uyghur_latin_uly" text,
  "population_2010_census" text,
  "area_km" text,
  "density_km" text
);
SELECT "hanyu_pinyin" FROM "subdivisions" WHERE "area_km"='400';