Independent solution

How to solve this Duration and Convexity question

Setup

Setup

A level perpetuity with its first payment in year one has Macaulay duration one plus i divided by i.

DM=(51)+1.100.10=15D_M=(5-1)+\frac{1.10}{0.10}=15

Model

Model

Deferring the first payment from year one to year five shifts every payment time four years later.

Dmod=DM1+iD_{\mathrm{mod}}=\frac{D_M}{1+i}

Compute

Compute

The resulting Macaulay duration is 15; converting to modified duration divides by 1.10.

Dmod=151.10=13.6364D_{\mathrm{mod}}=\frac{15}{1.10}=13.6364

Answer

Answer

The modified duration is 13.64, corresponding to choice A.

Dmod13.64(A)\boxed{D_{\mathrm{mod}}\approx13.64\quad\text{(A)}}