Among the establishments that paid a 500 fine, what is the percentage of restaurants?
a 500 fine refers to fine = 500; restaurant refers to facility_type = 'Restaurant'; percentage = divide(count(license_no where facility_type = 'Restaurant'), count(license_no)) * 100% where fine = 500
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