問21
頻出度★☆☆
システム開発案件 A，B，C のうち，採算性があるものはどれか。ここで，採算検討の対象期間はシステムのサービス開始後の 5 年目までとし，サービス開始後は，毎年，システムのメンテナンス費用が初期投資額の 10％発生するものとする。 単位 百万円
| システム開発案件 | 初期投資額 | 毎年のシステム効果 |
|---|---|---|
| A | 250 | 80 |
| B | 450 | 140 |
| C | 700 | 200 |
平成22年度 春期 ITパスポート試験 問21
ストラテジ系システム企画 › システム化計画
This question's explanation and your answers so far.
解説
問 21
- ア
正解 The correct answer is ア (A and B). This is a calculation question that uses cost-effectiveness to judge whether the initial investment can be recovered within 5 years. First, the annual maintenance cost is 10% of the initial investment, so A=250×0.1=25, B=450×0.1=45, C=700×0.1=70 (million yen). Next, subtracting this maintenance cost from the annual system benefit gives the annual net benefit: A=80-25=55, B=140-45=95, C=200-70=130. Since the period considered runs up to the 5th year after the service starts, multiplying by 5 gives the cumulative net benefit: A=55×5=275, B=95×5=475, C=130×5=650. Finally, comparing with the initial investment: A gives 275-250=+25 and B gives 475-450=+25, so both exceed their investment and are profitable. C, on the other hand, gives 650-700=−50, so it cannot recover its investment within 5 years and is not profitable. Therefore the profitable projects are A and B, and ア is correct. The key of this question is that what you compare is not the benefit amount itself, but the “cumulative net benefit after subtracting the maintenance cost from the benefit” against the “initial investment.”
Incorrectイ
B and C. B has a 5-year cumulative net benefit of 475 against an initial investment of 450, giving +25, so it is profitable. C, however, has a 5-year cumulative net benefit of 650 against an initial investment of 700, falling 50 million yen short, so it cannot recover its investment within the period considered. Treating C as profitable is itself the error. C has the largest annual system benefit (200) of the three projects, so it looks favorable if you only look at the size of the benefit, but its initial investment of 700 and the maintenance cost of 70 that is proportional to it are also the largest, and 5 years of its net benefit of 130 still falls short.
Incorrectウ
C and A. A is +25 and is profitable, but C's 5-year cumulative net benefit of 650 does not reach its initial investment of 700, giving −50, so it is not profitable. On top of that, this option also wrongly leaves out B, which is profitable. C's payback period is 700÷130 ≒ 5.4 years, slightly beyond the 5th year that defines the period considered; if the period were 6 years the story would change, but under this question's conditions it is out of scope.
Incorrectエ
A, B, and C. A and B are profitable, but C has a 5-year cumulative net benefit of 650 against an initial investment of 700, giving −50, so it is not profitable. An option that treats all three projects as profitable fails to reflect the condition that the maintenance cost grows in proportion to the initial investment (70 per year for C). If you ignored the maintenance cost and simply added up 5 years of the annual system benefit, you would get A=400, B=700, C=1,000, which makes all three look as if they exceed their investment, but that calculation ignores the conditions given in the question.
ここがポイント
- Cost-effectiveness is judged by comparing the “cumulative benefit minus cumulative cost over a given period” with the “initial investment.” In this question you first find annual net benefit = annual system benefit - annual maintenance cost, then judge profitability by whether 5 years of it exceeds the initial investment.
- When the maintenance cost is given as a ratio such as “10% of the initial investment,” a project with a larger investment also carries a proportionally heavier running cost. Do not judge only by the size of the benefit at introduction; it is important to evaluate with the TCO (Total Cost of Ownership) mindset, including operating costs as well.
用語