CREATE TABLE table_75770 ("County" TEXT, "Population  ( 2011 ) " FLOAT, "Population  ( 2006 ) " FLOAT, "Change  ( % ) " FLOAT, "Area  ( km\\u00b2 ) " FLOAT, "Population density" FLOAT)

What was the Area (km ) when the Population (2011) was 8574, and the Population density was larger than 381.4?
SELECT AVG("Area (km\u00b2)") FROM table_75770 WHERE "Population (2011)" = '8574' AND "Population density" > '381.4'
SELECT AVG("Area (km\u00b2)") FROM "table_75770" WHERE "Population (2011)" = '8574' AND "Population density" > '381.4'