For the business whose business certificate number is 304977, how many violations did it have on 2013/10/7?
date = '2013-10-07';
SELECT COUNT(T1.business_id) FROM violations AS T1 INNER JOIN businesses AS T2 ON T1.business_id = T2.business_id WHERE T2.business_certificate = '304977' AND T1.`date` = '2013-10-07'