This question's explanation and your answers so far.
与信限度額が3,000万円に設定されている取引先の5月31日業務終了時までの全取引が表のとおりであるとき，その時点での取引先の与信の余力は何万円か。ここで，受注分も与信に含めるものとし，満期日前の手形回収は回収とはみなさないものとする。
| 取引 | 日付 | 取引内訳 | 取引金額 | 備考 |
|---|---|---|---|---|
| 取引① | 4/2 | 売上計上 | 400万円 | |
| 5/31 | 現金回収 | 400万円 | ||
| 取引② | 4/10 | 売上計上 | 300万円 | |
| 5/10 | 手形回収 | 300万円 | 満期日：6/10 | |
| 取引③ | 5/15 | 売上計上 | 600万円 | |
| 取引④ | 5/20 | 受注 | 200万円 |
1,100 man-yen is exactly the credit used (the portion already consumed against the limit) itself, not the “remaining credit” being asked about. The remaining credit is what is left after subtracting the used amount of 1,100 man-yen from the limit of 3,000 man-yen, so giving 1,100 as the answer confuses the used amount with the remaining credit.
正解 The remaining credit is found by “credit limit − credit used”. Tally the credit used as of the close of business on May 31, transaction by transaction. Transaction 1: the 400 man-yen recorded as sales was collected in cash on the same day and is fully collected, so the used amount is 0 man-yen. Transaction 2: the 300 man-yen recorded as sales was collected by bill on 5/10, but a bill collected before its due date of 6/10 is “not regarded as collection”, so the 300 man-yen remains as credit used. Transaction 3: the 600 man-yen recorded as sales is uncollected, so it is 600 man-yen. Transaction 4: the order received of 200 man-yen is 200 man-yen, because orders are also included in credit. Therefore the credit used is 0＋300＋600＋200＝1,100 man-yen. The remaining credit is 3,000−1,100＝1,900 man-yen, so the correct answer is イ.
2,200 man-yen is the value obtained if the 300 man-yen bill collection in Transaction 2 is treated as a valid collection and removed from the used amount (used ＝ 600＋200＝800, 3,000−800＝2,200). However, this overlooks the rule that a bill collected before its due date (5/10, before 6/10) is not regarded as collection, so it is wrong.
2,400 man-yen is the value obtained if the bill collection in Transaction 2 is treated as already collected and the 200 man-yen order in Transaction 4 is forgotten from credit (counting only Transaction 3’s 600 man-yen as the used amount, 3,000−600＝2,400). This overlooks both the bill rule and the condition that orders are also included in credit.