Independent solution

How to solve this Equivalent Discount Rate over Mixed Interest Regimes question

Setup

Setup

Accumulate the principal through the first two effective-rate years.

A2=100(1.05)2A_2=100(1.05)^2

Model

Model

Integrate the later force from time 2 through time 5.

exp(25dt1+t)=63=2\exp\left(\int_2^5\frac{dt}{1+t}\right)=\frac63=2

Compute

Compute

The terminal amount is 220.50. Define a constant annual effective discount over all five years.

A5=220.50A_5=220.50
100=220.50(1d)5100=220.50(1-d)^5

Answer

Answer

Solving gives 14.627%, choice C.

d=1(100220.50)1/5=0.1462744d=1-\left(\frac{100}{220.50}\right)^{1/5}=0.1462744
d14.6%(C)\boxed{d\approx14.6\%\quad\text{(C)}}