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_21550897_1 (production_code INTEGER, us_viewers__million_ VARCHAR)
### Question:
What is the production code for the episode that had 9.18 million viewers (U.S.)?
### Answer:
SELECT MAX(production_code) FROM table_21550897_1 WHERE us_viewers__million_ = "9.18"