When was the season finale that ranked 20th?
CREATE TABLE table_29637 (
    "Season" text,
    "Episodes" real,
    "Timeslot ( EST )" text,
    "Season premiere" text,
    "Season finale" text,
    "TV season" text,
    "Rank" text,
    "Viewers (in millions)" text
)
SELECT "Season finale" FROM table_29637 WHERE "Rank" = '20th'
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: When was the season finale that ranked 20th? ### Input: CREATE TABLE table_29637 (
    "Season" text,
    "Episodes" real,
    "Timeslot ( EST )" text,
    "Season premiere" text,
    "Season finale" text,
    "TV season" text,
    "Rank" text,
    "Viewers (in millions)" text
) ### Response: SELECT "Season finale" FROM table_29637 WHERE "Rank" = '20th'