Among all films that the customer RUTH MARTINEZ has rented, what is the percentage of it being a Music film?
music film refers to name = 'Music'; percentage = Divide (Count(film_id where name = 'Music'), Count(film_id)) * 100
SELECT CAST(SUM(IIF(T3.name = 'Music', 1, 0)) AS REAL) * 100 / COUNT(T1.film_id) FROM film AS T1 INNER JOIN film_category AS T2 ON T1.film_id = T2.film_id INNER JOIN category AS T3 ON T2.category_id = T3.category_id INNER JOIN inventory AS T4 ON T1.film_id = T4.film_id INNER JOIN customer AS T5 ON T4.store_id = T5.store_id INNER JOIN rental AS T6 ON T4.inventory_id = T6.inventory_id WHERE T5.first_name = 'RUTH' AND T5.last_name = 'MARTINEZ'