What is the production code for episode #78?
CREATE TABLE table_3515 (
    "Episode #" text,
    "Season Episode #" text,
    "Title" text,
    "Directed by" text,
    "Written by" text,
    "Original air date" text,
    "Prod. code" text
)
SELECT "Prod. code" FROM table_3515 WHERE "Episode #" = '78'
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 production code for episode #78? ### Input: CREATE TABLE table_3515 (
    "Episode #" text,
    "Season Episode #" text,
    "Title" text,
    "Directed by" text,
    "Written by" text,
    "Original air date" text,
    "Prod. code" text
) ### Response: SELECT "Prod. code" FROM table_3515 WHERE "Episode #" = '78'