In films with a rental rate of 2.99, how many of the films are starred by Nina Soto?
a rental rate of 2.99 refers to rental_rate = 2.99
SELECT COUNT(T1.film_id) FROM film_actor AS T1 INNER JOIN actor AS T2 ON T1.actor_id = T2.actor_id INNER JOIN film AS T3 ON T1.film_id = T3.film_id WHERE T3.rental_rate = 2.99 AND T2.first_name = 'Nina' AND T2.last_name = 'Soto'