How many air dates does the episode with 15.50 million viewers have? 
CREATE TABLE table_26198709_1 (original_air_date VARCHAR, us_viewers__million_ VARCHAR)
SELECT COUNT(original_air_date) FROM table_26198709_1 WHERE us_viewers__million_ = "15.50"
<s>[INST] Write mssql query to answer the following question given the database schema. Schema: CREATE TABLE table_26198709_1 (original_air_date VARCHAR, us_viewers__million_ VARCHAR) Question: How many air dates does the episode with 15.50 million viewers have?  [/INST] SELECT COUNT(original_air_date) FROM table_26198709_1 WHERE us_viewers__million_ = "15.50" </s>