CREATE TABLE table_40539 ("Date" TEXT, "Cover model" TEXT, "Centerfold model" TEXT, "Interview subject" TEXT, "20 Questions" TEXT)

Which Cover model has a Centerfold model of scarlett keegan?
SELECT "Cover model" FROM table_40539 WHERE "Centerfold model" = 'scarlett keegan'
SELECT "Cover model" FROM "table_40539" WHERE "Centerfold model" = 'scarlett keegan'