How much is the total amount of sales handled by Heather McBadden?
total amount of sales = SUM(MULTIPLY(Quantity, Price));
SELECT SUM(T2.Quantity * T3.Price) FROM Employees AS T1 INNER JOIN Sales AS T2 ON T1.EmployeeID = T2.SalesPersonID INNER JOIN Products AS T3 ON T2.ProductID = T3.ProductID WHERE T1.FirstName = 'Heather' AND T1.LastName = 'McBadden'