What is the highest production code when the writer was brian egeston after season 5?
CREATE TABLE table_57421 (
    "Series #" real,
    "Season #" real,
    "Title" text,
    "Directed by" text,
    "Written by" text,
    "Original air date" text,
    "Production code" real
)
SELECT MAX("Production code") FROM table_57421 WHERE "Written by" = 'brian egeston' AND "Season #" > '5'
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: What is the highest production code when the writer was brian egeston after season 5? ### Input: CREATE TABLE table_57421 (
    "Series #" real,
    "Season #" real,
    "Title" text,
    "Directed by" text,
    "Written by" text,
    "Original air date" text,
    "Production code" real
) ### Response: SELECT MAX("Production code") FROM table_57421 WHERE "Written by" = 'brian egeston' AND "Season #" > '5'