With the increasing labor quantity the profit may increase after a certain quantity, which means the deficit will be substituted by the benefit in forge process of screw. So that through turnover to be established the benefit may be formed after turn point. Detail value is needed to calculate the field according to the curves between them. The TC and AC is the first factor to consider and then AVC and AFC which is second factor. The profit point is 5.5 and 20.5 piece when labor is two. That means that in the scope of this field the profit may be available. When the labor and capital inclines the total cost will incline. Average cost is no proportion to total cost.