Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_21501564_1 (theme VARCHAR, original_artist VARCHAR)
### Question:
How many weeks featured duffy as the original artist?
### Answer:
SELECT COUNT(theme) FROM table_21501564_1 WHERE original_artist = "Duffy"