Write SQL query to solve given problem: What is the the average percentage of profit for the all the product?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT AVG((T1.ListPrice - T2.StandardCost) * 100 / T2.StandardCost) FROM ProductListPriceHistory AS T1 INNER JOIN ProductCostHistory AS T2 ON T1.ProductID = T2.ProductID