How many episodes had an original air date with 5.1 million viewers
CREATE TABLE table_15938543_1 (
    original_air_date VARCHAR,
    us_viewers__million_ VARCHAR
)
SELECT COUNT(original_air_date) FROM table_15938543_1 WHERE us_viewers__million_ = "5.1"
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: How many episodes had an original air date with 5.1 million viewers ### Input: CREATE TABLE table_15938543_1 (
    original_air_date VARCHAR,
    us_viewers__million_ VARCHAR
) ### Response: SELECT COUNT(original_air_date) FROM table_15938543_1 WHERE us_viewers__million_ = "5.1"