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_17641206_4 (duration VARCHAR, written_by VARCHAR)
### Question:
How many episodes  of 30 minutes were written by John Sullivan?
### Answer:
SELECT COUNT(duration) FROM table_17641206_4 WHERE written_by = "John Sullivan"