which is the biggest production code?
CREATE TABLE table_73415 (
    "Season no." real,
    "Series no." real,
    "Title" text,
    "Directed by" text,
    "Written by" text,
    "Original air date" text,
    "Production code" real,
    "U.S. Viewers (millions)" text
)
SELECT MAX("Production code") FROM table_73415
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: which is the biggest production code? ### Input: CREATE TABLE table_73415 (
    "Season no." real,
    "Series no." real,
    "Title" text,
    "Directed by" text,
    "Written by" text,
    "Original air date" text,
    "Production code" real,
    "U.S. Viewers (millions)" text
) ### Response: SELECT MAX("Production code") FROM table_73415