Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
What was the ranking of the season whose finale aired on May 15, 2011?

### Inputs:
table_name: table, columns: ['Season', 'Season premiere', 'Season finale', 'TV season', 'Ranking', 'Viewers (in millions)']

### Response:
SELECT Ranking FROM table WHERE Season finale = may 15, 2011