4, according to the lathe and planer two processes processing A, B, C, D four parts, need to follow the lathe and planer two processes processing (the first lathe after the planer) The time required is shown in hours as follows
1 hour later (after 12 hours) A lathe well, then planer, this time lathe Ding;
7 hours later (after 11 hours) B spare parts good, 1 hour left a lathe good;
First lathe B 4 hours then planer B, while lathe a;
6 hours later (after 18 hours) a good parts, Ding parts also just finished the car, digging machine Ding, then lathe C;
