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 museum (num_of_staff INTEGER, open_year INTEGER)
### Question:
Find the average number of staff working for the museums that were open before 2009.
### Answer:
SELECT AVG(num_of_staff) FROM museum WHERE open_year < 2009