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