How many different total number of transit passengers are there in London Luton?
CREATE TABLE table_13836704_7 (
    transit_passengers VARCHAR,
    airport VARCHAR
)
SELECT COUNT(transit_passengers) FROM table_13836704_7 WHERE airport = "London Luton"
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 different total number of transit passengers are there in London Luton? ### Input: CREATE TABLE table_13836704_7 (
    transit_passengers VARCHAR,
    airport VARCHAR
) ### Response: SELECT COUNT(transit_passengers) FROM table_13836704_7 WHERE airport = "London Luton"