CREATE TABLE table_17980 ("Member countries" TEXT, "Population" FLOAT, "Area  ( km\\u00b2 ) " FLOAT, "GDP  ( billion US$ ) " TEXT, "GDP per capita  ( US$ ) " FLOAT)

What is the gdp of the country with an area of 83871 (km2)?
SELECT "GDP (billion US$)" FROM table_17980 WHERE "Area (km\u00b2)" = '83871'
SELECT "GDP (billion US$)" FROM "table_17980" WHERE "Area (km\u00b2)" = '83871'