CREATE TABLE table_50900 ("Team" TEXT, "Coach" TEXT, "Home Ground" TEXT, "Location" TEXT, "Founded" TEXT)

Which team has an unknown coach and location of Athelstone?
SELECT "Team" FROM table_50900 WHERE "Coach" = 'unknown' AND "Location" = 'athelstone'
SELECT "Team" FROM "table_50900" WHERE "Coach" = 'unknown' AND "Location" = 'athelstone'