How many episodes were written only by William N. Fordes?
CREATE TABLE table_17488 (
    "Series #" real,
    "Season #" real,
    "Title" text,
    "Directed by" text,
    "Written by" text,
    "Original air date" text,
    "Production code" text,
    "U.S. viewers (millions)" text
)
SELECT COUNT("Series #") FROM table_17488 WHERE "Written by" = 'William N. Fordes'
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 episodes were written only by William N. Fordes? ### Input: CREATE TABLE table_17488 (
    "Series #" real,
    "Season #" real,
    "Title" text,
    "Directed by" text,
    "Written by" text,
    "Original air date" text,
    "Production code" text,
    "U.S. viewers (millions)" text
) ### Response: SELECT COUNT("Series #") FROM table_17488 WHERE "Written by" = 'William N. Fordes'