Independent solution

How to solve this Equation of Value with Quarterly Deposits question

Setup

Setup

Convert 4.2% nominal monthly to a monthly rate of 0.0035. Quarterly deposits occur every three months, and exactly forty-one occur before month 124.

jm=0.042/12=0.0035,1+jq=(1.0035)3j_m=0.042/12=0.0035,\quad1+j_q=(1.0035)^3

Model

Model

Value all deposits and the terminal target at time 0. The immediate amount X remains undiscounted, each 100 deposit is discounted 3k months, and 1.9X is discounted 124 months.

41 deposits occur before month 124\text{41 deposits occur before month }124

Compute

Compute

Only choice C has the correct deposit count and exponents, so it is the valid equation of value.

X+k=141100(1.0035)3k=1.9X(1.0035)124X+\sum_{k=1}^{41}\frac{100}{(1.0035)^{3k}}=\frac{1.9X}{(1.0035)^{124}}

Answer

Answer

The calculation gives X +∑ 3k for equation of value with quarterly deposits, matching published choice C.

choice C(C)\boxed{\text{choice C}\quad\text{(C)}}