Question: Among the users that permit the company to send regular emails to them, how many of them had made a transaction with a Visa card in July, 2014?
SQL: SELECT COUNT(T1.CustomerID) FROM customers AS T1 INNER JOIN `transaction` AS T2 ON T1.CustomerID = T2.CustomerID WHERE T1.SubscribedToEmailList = 'TRUE' AND T2.CreditCardType = 'Visa' AND STRFTIME('%Y-%m', T2.TransactionDate) = '2014-07'