Jan Corp. amended its defined benefit pension plan on January 1, granting a total credit of $180,000 to four employees for services rendered prior to the plan's adoption. The employees, A, B, C, and D, are expected to retire from the company as follows:

"A" will retire after three years

"B" and "C" will retire after six years

"D" will retire after nine years

What is the amount of prior service cost amortization in the first year under U.S. GAAP?

A. $0

• B. $45,000
• C. $20,000
• D. $30,000