Write SQL query to solve given problem: Among the establishments that paid a 500 fine, what is the percentage of restaurants?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT CAST(COUNT(CASE WHEN T1.facility_type = 'Restaurant' THEN T1.license_no END) AS REAL) * 100 / COUNT(T1.facility_type) FROM establishment AS T1 INNER JOIN inspection AS T2 ON T1.license_no = T2.license_no INNER JOIN violation AS T3 ON T2.inspection_id = T3.inspection_id WHERE T3.fine = 500