Write SQL query to solve given problem: How many Folsom customers prefer to pay with Visa?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT COUNT(T1.CustomerID) FROM customers AS T1 INNER JOIN `transaction` AS T2 ON T1.CustomerID = T2.CustomerID WHERE T1.City = 'Folsom' AND T2.CreditCardType = 'Visa'