This question's explanation and your answers so far.
ある販売会社が扱っている商品の4月末の実在庫数が100個であり, 5月10日までの受発注取引は表のとおりである。商品は発注日の5日後に入荷するものとし, 販売会社と商品発注先の休日, 及び前月以前の受発注取引を考えない場合, 5月10日時点の引当可能在庫数は何個か。ここで, 引当可能在庫数とは, その時点の在庫のうち引当可能な数量とする。
| 取引日 | 商品の受注 | 商品の発注 |
|---|---|---|
| 5月2日 | 40個 | - |
| 5月3日 | - | 50個 |
| 5月6日 | 20個 | - |
| 5月7日 | - | 50個 |
| 5月9日 | 30個 | - |
正解 The correct answer is ア (60 units). Allocatable inventory means the quantity of stock on hand at that point in time that has not yet been assigned to any sales order already received and can still be allocated to new orders. It is therefore obtained by subtracting the quantity already committed to received orders from the inventory that may be counted at that point, including deliveries that have already arrived. First, fix the inventory side. The starting point is the actual inventory of 100 units at the end of April. Because ordered goods arrive 5 days after the order date, the 50 units ordered on May 3 arrive on May 8 and are already on hand as of May 10. On the other hand, the 50 units ordered on May 7 arrive on May 12, so they have not been delivered as of May 10 and cannot be added to the inventory. The inventory that may be counted as of May 10 is therefore 100 + 50 = 150 units. Next, fix the allocated side. Every sales order received is a quantity promised for delivery to a customer, so that much stock is reserved (allocated) and cannot be used for other orders. Adding the 40 units of May 2, the 20 units of May 6, and the 30 units of May 9 gives 40 + 20 + 30 = 90 units already allocated. Hence allocatable inventory = 150 − 90 = 60 units, and ア is correct. Following the table in chronological order, judging whether goods have arrived by their arrival date, and not mixing up the directions — a sales order received holds inventory down (allocation), while a purchase order placed increases it (arrival) — are the keys to this calculation.
90 units is the value obtained when the inventory side is computed correctly as 100 + 50 = 150 units, but only the 40 units of May 2 and the 20 units of May 6 — 60 units in total — are counted as allocated sales orders, missing the 30 units received on May 9 (150 − 60 = 90). May 9 is a transaction earlier than May 10, so those 30 units are of course already allocated at that point, and there is no reason to leave them out of the total. Sales orders received carry no lead-time condition of the kind that applies to arrivals, so every order whose transaction date is on or before the reference point must be subtracted as already allocated.
110 units is the value obtained when the 90 units of sales orders are subtracted correctly, but both purchase orders totalling 100 units (50 units on May 3 and 50 units on May 7) are added to the inventory as if they had already arrived (100 + 50 + 50 − 90 = 110). However, under the condition that goods arrive 5 days after the order date, the order placed on May 7 arrives on May 12 and is not yet on hand as of May 10. Goods that have not been delivered cannot be counted as current inventory, so this is wrong. Reflecting the procurement lead time in the inventory calculation is the key point of this question.
140 units is the value obtained when the May 7 purchase order is also treated as already arrived, overstating the inventory as 100 + 50 + 50 = 200 units, and on top of that the 30 units received on May 9 are forgotten in the subtraction, giving 200 − 60 = 140. It combines both mistakes — including goods that have not arrived in the inventory, and missing an allocated sales order — and gives the largest estimate of inventory. Allocating on the basis of this figure would mean promising customers stock that does not actually exist, leading to stockouts or late deliveries.