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_58 (age_at_appointment INTEGER, portfolio_attachment VARCHAR)
### Question:
What is the average age at appointment of those attached to security?
### Answer:
SELECT AVG(age_at_appointment) FROM table_name_58 WHERE portfolio_attachment = "security"