What is the average monthly circulating supply for Frozen in 2014.
average monthly circulating supply = AVG(circulating_supply); in 2017 refers to date BETWEEN '2017-01-01' AND '2017-12-31'
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'