中會退休金問題 - 會計

Derosa Company has a defined benefit pension plan for its employees. Prior to
1992, the company has not had an additional pension liability. At the end of
1992, the company's acturay developed the fallowing information regarding its
pension plan

PBO $1,429,000
ABO 987,000
Plan Asset(FV) 852,000
Unrecognized prior service cost 200,000
Required:
Caculate the additional pension liability required at the end of 1992 and
prepare the appropriate journal entry, assuming that the comapny had an
unfunded accrued pension cost(liability) of $75,000 before considering the
preceding information.

解:
ABO $987,000
Plan Asset(FV) (852,000)
----------
Unfunded ABO $135,000
Unfunded accrued pension cost (75,000)
----------
Additional pension liability $60,000


1992 Deferred Pension Cost 60,000
Additional Pension Liability 60,000

請問為什麼使用ABO而非PBO呢?
為什麼未認列前期服務成本沒有算入呢?
還有Additional Pension Liability指的是"應計退休金負債"嗎?

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