The relationship between investment and shares is established to find the intrinsic nature. It is found when the best labour is 6 the cost is low and the number of shares are 1000 with the intersection of 1 RMB which is turnover point. When the best capital is 1RMB the cost will be 70 RMB and the turnover point is 600 of the number of shares with the 5 RMB. Since Pl>Pk they are the least when the total product is bigger too. The biggest average product has been from 2,000 to 5,500 pieces while the biggest total product may be an arrangement of 7,000 and 40,000 pieces. The least total cost may be 150Yuan/one. Pk is bigger the least cost is good.