Write SQL query to solve given problem: Among all the active customers, how many of them live in Arlington?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT COUNT(T2.customer_id) FROM address AS T1 INNER JOIN customer AS T2 ON T1.address_id = T2.address_id INNER JOIN city AS T3 ON T1.city_id = T3.city_id WHERE T2.active = 1 AND T3.city = 'Arlington'