Write SQL query to solve given problem: What was the average price of a Bitcoin in the year 2013?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT AVG(T2.price) FROM coins AS T1 INNER JOIN historical AS T2 ON T1.id = T2.coin_id WHERE STRFTIME('%Y', T2.date) = '2013' AND T1.name = 'Bitcoin'