Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_24961421_1 (written_by VARCHAR, us_viewers__millions_ VARCHAR)
### Question:
Who wrote the episode that had 12.15 million viewers?
### Answer:
SELECT written_by FROM table_24961421_1 WHERE us_viewers__millions_ = "12.15"