First Principles Thinking: Money Duration Formula
A is correct. Money duration measures dollar price change per 1% yield change: \( MoneyDur = ModDur \times Market\,Value \). Market value = \( 10,000,000 \times 0.98 = 9,800,000 \). Thus \( MoneyDur = 5 \times 9,800,000 = 49,000,000 \) per 100% yield change. Per 1% (0.01) yield change: \( 49,000,000 \times 0.01 = 490,000 \). Alternatively, \( MoneyDur = 5 \times 9,800,000 = \$490,000 \) directly (modified duration already incorporates the "per unit yield change" scaling). Mental check: 5% of USD 9.8M ≈ 490k. Money duration converts percentage sensitivity into dollar terms, enabling position-level risk management and is essential for hedging calculations where absolute dollar exposure matters more than percentage changes.
B is incorrect because USD 500,000 uses par value (10M) instead of market value (USD 9.8M): \( 5 \times 10,000,000 \times 0.01 = 500,000 \). Bond risk metrics must use current market value, not face value, because price changes occur from current levels, not par. A bond trading at 98 has less dollar value at risk than one at 100, so using par overstates money duration by approximately 2%.
C is incorrect because USD 5,000,000 results from forgetting to scale by the yield change magnitude or misunderstanding money duration units. This equals 50% of the market value, which would only occur for a 10% (1,000 bp) yield change: \( 5 \times 0.10 = 0.50 = 50\% \). Money duration should reflect a standard 1% yield change, not 10%, making this answer 10x too large.