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 department (num_employees INTEGER, ranking INTEGER)
### Question:
What is the average number of employees of the departments whose rank is between 10 and 15?
### Answer:
SELECT AVG(num_employees) FROM department WHERE ranking BETWEEN 10 AND 15