What date did the episode air that had n/a for it's bbc three weekly ranking?
CREATE TABLE table_24399615_4 (airdate VARCHAR, bbc_three_weekly_ranking VARCHAR)
SELECT airdate FROM table_24399615_4 WHERE bbc_three_weekly_ranking = "N/A"
<s>[INST] Write mssql query to answer the following question given the database schema. Schema: CREATE TABLE table_24399615_4 (airdate VARCHAR, bbc_three_weekly_ranking VARCHAR) Question: What date did the episode air that had n/a for it's bbc three weekly ranking? [/INST] SELECT airdate FROM table_24399615_4 WHERE bbc_three_weekly_ranking = "N/A" </s>