A part can be machined in 30 minutes on the engine lathe where as it can be machined in 6 minutes on a turret lathe. However, it would cost additionally Rs. 500 to tool up the turret lathe for the operation. If the hourly rate including labour and overhead is Rs. 80 for the engine lathe and Rs. 160 for the turret lathe, The minimum number of parts required to make the turret lathe more economical to use, for the operation