Among the classic movies, how many movies have a rental rate of less than 1?
classic movie refers to name = 'Classics'; rental rate of less than 1 refers to rental_rate < 1; movie refers to film_id
SELECT COUNT(T1.film_id) FROM film_category AS T1 INNER JOIN category AS T2 ON T1.category_id = T2.category_id INNER JOIN film AS T3 ON T1.film_id = T3.film_id WHERE T3.rental_rate < 1 AND T2.name = 'Classics'