CREATE TABLE table_15924 ("Season" TEXT, "Network" TEXT, "Season premiere" TEXT, "Season finale" TEXT, "TV season" TEXT, "Ranking" TEXT, "Viewers  ( in millions ) " TEXT)

What was the ranking of the season finale aired on May 8, 2006?
SELECT "Ranking" FROM table_15924 WHERE "Season finale" = 'May 8, 2006'
SELECT "Ranking" FROM "table_15924" WHERE "Season finale" = 'May 8, 2006'