pre_text: The following table presents cumulative items not recognized as a component of net periodic benefits expense as of December 31, 2017, items recognized as a component of net periodic benefits expense in 2018, additional items deferred during 2018 and cumulative items not recognized as a component of net periodic benefits expense as of December 31, 2017. The items not recognized as a component of net periodic benefits expense have been recorded on our consolidated balance sheets in accumulated other comprehensive loss: (1) Amounts currently recognized in net periodic benefits expense include $375 million of benefit arising from the adoption of ASU 2018-02. See Note 1— Background and Summary of Significant Accounting Policies for further detail. (2) Amounts currently recognized in net periodic benefits expense include $32 million arising from the adoption of ASU 2018-02. See Note 1— Background and Summary of Significant Accounting Policies for further detail.
table: As of and for the Years Ended December 31,
table: 2017 Recognition of Net Periodic Benefits Expense Deferrals Net Change in AOCL 2018
table: (Dollars in millions)
table: Accumulated other comprehensive loss:
table: Pension plans:
table: Net actuarial (loss) gain $(2,892) 179 (260) (81) (2,973)
table: Prior service benefit (cost) 54 (8) — (8) 46
table: Deferred income tax benefit (expense)(1) 1,107 (418) 65 (353) 754
table: Total pension plans (1,731) (247) (195) (442) (2,173)
table: Post-retirement benefit plans:
table: Net actuarial (loss) gain (250) — 257 257 7
table: Prior service (cost) benefit (107) 20 — 20 (87)
table: Deferred income tax benefit (expense)(2) 122 (37) (63) (100) 22
table: Total post-retirement benefit plans (235) (17) 194 177 (58)
table: Total accumulated other comprehensive loss $(1,966) (264) (1) (265) (2,231)
question: Analyse this data from a financial earnings document. What is the sum of the prior service benefit (cost) for pension plans in 2017 and 2018?