Bài tập nâng cao môn logistics và quản lý chuỗi cung ứng. Bài tập liên quan đến việc tính toán chi phí nhằm đưa ra quyết định nhằm tối ưu chuỗi cung ứng. Các công thức được áp dụng chặt chẽ và giải thích dễ hiểu, rõ ràng. Bài toán có thể áp dụng trong thực tế các công ty khi phân phối giao hàng.
Logistics Exercise_Honor Program Full Name: Le Thi Ngoc Anh Student code: K194020123 EXERCISE The KTDN pharmacy has twenty-five retail outlets in Saigon The current policy is to carry every drug in each retail outlet KTDN is investigating the possibility of centralizing some of the drugs in one location Delivery charge would increase by $0.02 per unit if a drug were centralized The increase in delivery charge comes from the additional cost of operating the shuttle from the central location to each of the other locations At each retail outlet, KTDN follows a periodic review policy with weekly replenishment (a replenishment order is placed once every seven days) The replenishment lead time is three days KTDN plans to stick to once-a-week ordering even if a drug is centralized KTDN uses an inventory holding cost of 20% and aims for a cycle service level of 99 percent (hence, z-score = 2.33) Assume that demand across stores is independent a Consider a drug with daily demand at each store that is normally distributed, with a mean of 300 and a standard deviation of 50 The drug costs $10 per unit What is the annual holding cost of safety inventory across all retail stores? If the drug were centralized in one location, what would the annual cost of holding safety inventory at the central location be? What would the annual increase in delivery charge be? Do you recommend centralization? b Now consider a drug with daily demand at each store that is normally distributed, with a mean of and a standard deviation of The drug costs $10 per unit What is the annual holding cost of safety inventory across all retail stores? If the drug were centralized in one location, what would the annual cost of holding safety inventory at the central location be? What would the annual increase in delivery charge be? Do you recommend centralization? Problem Summary: - There are 25 retail outlets - Current policy: carry every drug in each retail outlet (Decentralized) • • • • Review policy: periodic review policy T = days (weekly replenishment) L = days (lead time) h = 20% (inventory holding cost) • Cycle service level = 99% ➔ z = 2.33 If centralizing: Delivery charge increase = $0.02 per unit Assume that demand across stores is independent ANSWERS a) 300 units D (mean of daily demand) 𝛔D (standard deviation of demand) c (drug cost per unit) 50 units $10 What is the annual holding cost of safety inventory across all retail stores? With decentralized option: Total safety inventory (stock): SS = 𝒛 ∗ √(𝐋 + 𝐓) ∗ ∑𝟐𝟓 𝒊=𝟏 𝝈i = 2.33*sqrt(7+3)*50*25 = 9210 (units) ➔ Annual holding cost of safety stock in this case: = SS*h*c = 9210*10*0.2 = $18420 With centralized option: Safety stock on aggregation: SS = 𝒛 ∗ √(𝐋 + 𝐓) ∗ 𝛔CD = 𝑧 ∗ √(L + T) ∗ √k ∗ σi = 2.33*sqrt(10)*sqrt(25)*50 = 1842 (units) ➔ Annual holding cost of safety stock in this case: = SS*h*c = 1842*0.2*10 = $3684 What would the annual increase in delivery charge be? with D = 300/day/outlet, 25 outlets, year = 365 days, delivery charge increase = 0.02/unit, Annual increase in delivery charge = 300*25 *365*0.02 = $54750 Do you recommend centralization? Cost difference when adopt centralized option (in comparison with decen option): = Annual delivery charge increase + Annual holding cost of SS (centralized) – Annual holding cost of SS (decentralized) = 54750 +3684 – 18420 = $40014 ➔ Don’t Recommend: Because centralized model costs higher in term of holding cost and delivery charge b) D (mean of daily demand) 𝛔D (standard deviation of demand) c (drug cost per unit) units units $10 What is the annual holding cost of safety inventory across all retail stores? With decentralized option: Total safety inventory (stock): SS = 𝒛 ∗ √(𝐋 + 𝐓) ∗ ∑𝟐𝟓 𝒊=𝟏 𝝈i = 2.33*sqrt(7+3)*4*25 = 737 (units) ➔ Annual holding cost of safety stock in this case: = SS*h*c = 737*10*0.2 = $1474 With centralized option: Safety stock on aggregation: SS = 𝒛 ∗ √(𝐋 + 𝐓) ∗ 𝛔CD = 𝑧 ∗ √(L + T) ∗ √k ∗ σi = 2.33*sqrt(10)*sqrt(25)*4 = 147 (units) ➔ Annual holding cost of safety stock in this case: = SS*h*c = 147*0.2*10 = $294 What would the annual increase in delivery charge be? with D = 5/day/outlet, 25 outlets, year = 365 days, delivery charge increase = 0.02/unit, Annual increase in delivery charge = 5*25 *365*0.02 = $912.5 Do you recommend centralization? Cost difference when adopt centralized option (in comparison with decen option): = Annual delivery charge increase + Annual holding cost of SS (centralized) – Annual holding cost of SS (decentralized) = 912.5 +294 – 1474 = - $267.5 ➔ Recommend: because centralized option costs lower in term of holding cost and delivery charge