user: Question: What was the ranking of the season whose finale aired on May 15, 2011?
Columns: ['Season', 'Season premiere', 'Season finale', 'TV season', 'Ranking', 'Viewers (in millions)']
Types: ['text', 'text', 'text', 'text', 'text', 'real']
Sample row: ['1', 'December 3, 2003', 'August 18, 2004', '2003–2004', '#41', 10.63]
SQL:

assistant: SELECT "Ranking" FROM "Table" WHERE "Season finale" = 'May 15, 2011';