What is the average selling price of different vendors of the product Hex Nut 5?
average selling price = divide(sum(StandardPrice), count(BusinessEntityID))
SELECT SUM(T1.StandardPrice) / COUNT(T1.BusinessEntityID) FROM ProductVendor AS T1 INNER JOIN Product AS T2 ON T1.ProductID = T2.ProductID WHERE T2.Name = 'Hex Nut 5'