List the full name of customers who spend more than 50,000 in descending order the amount spend.
full name of the customer = FirstName, MiddleInitial, LastName; more than 50,000 in the amount refers to MULTIPLY(Quantity, Price) > 50000;
SELECT DISTINCT T3.FirstName, T3.MiddleInitial, T3.LastName FROM Products AS T1 INNER JOIN Sales AS T2 ON T1.ProductID = T2.ProductID INNER JOIN Customers AS T3 ON T2.CustomerID = T3.CustomerID WHERE T2.Quantity * T1.Price > 50000