Problem 4. A series system Consider the following series model. Stage 1 Stage 2 Stage 3 4-1. How many echelons are in the system? Please describe the composition of each echelon. 4-2. Assume that stage 3's ordering cost (A3), annual demand (D3), and holding cost (hy) are $100/item. 10000 items, and $200/item. What is the optimal order quantity at stage 3? 4-3. Assume that stage 2's ordering cost (A2) is 3 times of Az, while stage 2's holding cost (hy) is a quarter of hz. Then, what will be the optimal order quantity at stage 2 (indeed, find m2)? 4-4. (True/False) Optimal order quantity at stage I is always greater than equal to that of stage 2. Problem 4. A series system Consider the following series model. Stage 1 Stage 2 Stage 3 4-1. How many echelons are in the system? Please describe the composition of each echelon. 4-2. Assume that stage 3's ordering cost (A3), annual demand (D3), and holding cost (hy) are $100/item. 10000 items, and $200/item. What is the optimal order quantity at stage 3? 4-3. Assume that stage 2's ordering cost (A2) is 3 times of Az, while stage 2's holding cost (hy) is a quarter of hz. Then, what will be the optimal order quantity at stage 2 (indeed, find m2)? 4-4. (True/False) Optimal order quantity at stage I is always greater than equal to that of stage 2