Who was the writer for the episode with 2.15 million u.s.viewers?
CREATE TABLE table_24970 (
    "No. in series" real,
    "No. in season" real,
    "Title" text,
    "Directed by" text,
    "Written by" text,
    "Original air date" text,
    "Production code" text,
    "U.S. viewers (millions)" text
)
SELECT "Written by" FROM table_24970 WHERE "U.S. viewers (millions)" = '2.15'
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: Who was the writer for the episode with 2.15 million u.s.viewers? ### Input: CREATE TABLE table_24970 (
    "No. in series" real,
    "No. in season" real,
    "Title" text,
    "Directed by" text,
    "Written by" text,
    "Original air date" text,
    "Production code" text,
    "U.S. viewers (millions)" text
) ### Response: SELECT "Written by" FROM table_24970 WHERE "U.S. viewers (millions)" = '2.15'