What is the category for trains numbered 16609/16610?
CREATE TABLE table_21716139_1 (
    category VARCHAR,
    train_no VARCHAR
)
SELECT category FROM table_21716139_1 WHERE train_no = "16609/16610"
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: What is the category for trains numbered 16609/16610? ### Input: CREATE TABLE table_21716139_1 (
    category VARCHAR,
    train_no VARCHAR
) ### Response: SELECT category FROM table_21716139_1 WHERE train_no = "16609/16610"