Among the products from the mountain product line, how many of them are sold by over 2 vendors?
mountain product line refers to ProductLine = 'M'; sold by over 5 vendors refers to count(Name)>5
SELECT SUM(CASE WHEN T1.ProductLine = 'M' THEN 1 ELSE 0 END) FROM Product AS T1 INNER JOIN ProductVendor AS T2 ON T1.ProductID = T2.ProductID INNER JOIN Vendor AS T3 ON T2.BusinessEntityID = T3.BusinessEntityID GROUP BY T1.ProductID HAVING COUNT(T1.Name) > 2