What's the series number of the episode whose writer is David North?
CREATE TABLE table_24764 (
    "No. in series" real,
    "No. in season" real,
    "Title" text,
    "Directed by" text,
    "Written by" text,
    "Original air date" text,
    "U.S. viewers (millions)" text
)
SELECT MAX("No. in series") FROM table_24764 WHERE "Written by" = 'David North'
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's the series number of the episode whose writer is David North? ### Input: CREATE TABLE table_24764 (
    "No. in series" real,
    "No. in season" real,
    "Title" text,
    "Directed by" text,
    "Written by" text,
    "Original air date" text,
    "U.S. viewers (millions)" text
) ### Response: SELECT MAX("No. in series") FROM table_24764 WHERE "Written by" = 'David North'