What is the total number of episodes listed with a production code of 306?
CREATE TABLE table_18424435_4 (_number VARCHAR, production_code VARCHAR)
SELECT COUNT(_number) FROM table_18424435_4 WHERE production_code = 306
<s>[INST] Write mssql query to answer the following question given the database schema. Schema: CREATE TABLE table_18424435_4 (_number VARCHAR, production_code VARCHAR) Question: What is the total number of episodes listed with a production code of 306? [/INST] SELECT COUNT(_number) FROM table_18424435_4 WHERE production_code = 306 </s>