Among the Production Technicians who are single, how many of them are vendor contact?
Production Technicians refer to the  JobTitle = 'Production Technician%'; single refers to MaritalStatus = 'S'; Vendor contact refers to PersonType = 'VC'
SELECT COUNT(T1.BusinessEntityID) FROM Employee AS T1 INNER JOIN Person AS T2 ON T1.BusinessEntityID = T2.BusinessEntityID WHERE T1.JobTitle LIKE 'Production Technician%' AND T1.MaritalStatus = 'S' AND T2.PersonType = 'VC'