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_28138035_4 (womens_singles VARCHAR, year_location VARCHAR)
### Question:
Name the number of womens singles for 1999 rio de janeiro
### Answer:
SELECT COUNT(womens_singles) FROM table_28138035_4 WHERE year_location = "1999 Rio de Janeiro"