Write SQL query to solve given problem: What is the average actual profit by 1937 Lincoln Berline?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT SUM(T1.priceEach - T2.buyPrice) / COUNT(*) FROM orderdetails AS T1 INNER JOIN products AS T2 ON T1.productCode = T2.productCode WHERE T2.productName = '1937 Lincoln Berline'