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_name_20 (original_air_date INTEGER, series_number VARCHAR)
### Question:
What was the original air date of series number 10?
### Answer:
SELECT AVG(original_air_date) FROM table_name_20 WHERE series_number = 10