Of the products that has a reorder inventory point of no more than 600, how many manufactured in-house products that takes 1 day to manufacture with BOM Level 4 are there?
ReorderPoint<600; product is manufactured in-house refers to Makeflag = 1;
SELECT COUNT(T1.ProductID) FROM Product AS T1 INNER JOIN BillOfMaterials AS T2 ON T1.ProductID = T2.ProductAssemblyID WHERE T1.MakeFlag = 1 AND T1.DaysToManufacture = 1 AND T2.BOMLevel = 4 AND T1.ReorderPoint <= 600