CREATE TABLE table_57096 ("car plates  ( since 1937 ) " TEXT, "Voivodeship Separate city" TEXT, "Capital" TEXT, "Area in 1000km\\u00b2  ( 1930 ) " TEXT, "Population in 1000  ( 1931 ) " TEXT)

tell me the name of the capital with an area of 20,4.
SELECT "Capital" FROM table_57096 WHERE "Area in 1000km\u00b2 (1930)" = '20,4'
SELECT "Capital" FROM "table_57096" WHERE "Area in 1000km\u00b2 (1930)" = '20,4'