Which production code had original air dated february20,2011
CREATE TABLE table_28521 (
    "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 (million)" text
)
SELECT "Production code" FROM table_28521 WHERE "Original air date" = 'February20,2011'
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: Which production code had original air dated february20,2011 ### Input: CREATE TABLE table_28521 (
    "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 (million)" text
) ### Response: SELECT "Production code" FROM table_28521 WHERE "Original air date" = 'February20,2011'