The amount of prior service cost amortization for the years 2025 through 2030 using the years-of-service method would be $ 18, 750 per year.
How to find the service cost amortization?
Add up the total future years of service for all employees to get a baseline for distributing the pension plan amendment cost. Calculate the proportion of each employee's future service years relative to the total.
Distribute the $90,000 increase in projected benefit obligation proportionally over the future service years for each employee.
The service cost per employee is:
Kenneth:

Edward:

Donna:

Kevin:

Ruth:

Each employee's annual amortization from 2025 through 2030 is $3,750.
Since there are five employees, the total annual amount for the company is:
= 5 x 3, 750
= $ 18, 750
The employees and their Future Years of Service are:
Kenneth 3
Edward 4
Donna 5
Kevin 6
Ruth 6