Independent solution

How to solve this Duration and Convexity question

Setup

Setup

The immediate liability contributes value but zero to the duration numerator.

3.70=5(100000)v520000+100000v53.70=\frac{5(100000)v^5}{20000+100000v^5}

Model

Model

Use the stated weighted time to solve for the five-year discount factor and hence the annual yield factor.

v5=3.706.50,1+i=1.11929v^5=\frac{3.70}{6.50},\qquad 1+i=1.11929

Compute

Compute

Convert Macaulay duration to modified duration by dividing by one plus yield.

Dmod=3.701.11929=3.30567D_{\mathrm{mod}}=\frac{3.70}{1.11929}=3.30567

Answer

Answer

The modified duration is approximately 3.31 years, corresponding to choice B.

Dmod3.31(B)\boxed{D_{\mathrm{mod}}\approx3.31\quad\text{(B)}}