What is the average actual profit by 1937 Lincoln Berline?
average actual profit = AVG(SUBTRACT(priceEach, buyPrice)); 1937 Lincoln Berline is a product name;
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'