What is the production code of the episode written by Cathryn Humphris?
CREATE TABLE table_24938621_3 (production_code VARCHAR, written_by VARCHAR)
SELECT production_code FROM table_24938621_3 WHERE written_by = "Cathryn Humphris"
### Context: CREATE TABLE table_24938621_3 (production_code VARCHAR, written_by VARCHAR) ### Question: What is the production code of the episode written by Cathryn Humphris? ### Answer: SELECT production_code FROM table_24938621_3 WHERE written_by = "Cathryn Humphris"