What is the area of the nation with GDP per capita (US$) of 11,929?
CREATE TABLE "1973_enlargement" (
  "member_countries" text,
  "population" text,
  "area_km" text,
  "gdp_billion_us" text,
  "gdp_per_capita_us" text
);
SELECT "area_km" FROM "1973_enlargement" WHERE "gdp_per_capita_us"='11,929';