Write SQL query to solve given problem: What is the average monthly circulating supply for Frozen in 2014.. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT CAST(SUM(T2.circulating_supply) AS REAL) / 12 FROM coins AS T1 INNER JOIN historical AS T2 ON T1.id = T2.coin_id WHERE T1.name = 'Frozen' AND STRFTIME('%Y', T2.date) = '2014'