The following incomplete (columns have missing amounts) pension spreadsheet is for Old Tucson Corporation (OTC). Prior Net ($ in millions) debit (Credit) Beginning balance Service cost Interest cost Plan PBO Assets (520) Service (Gain) Pension Net Pension Expense Cash (Liability)/Asset Cost Lss 64 68 Expected return on assets Gain/loss on assets (25) (4) Amortization of: Prior service cost Net gain/ loss (8) Loss on PBO Contributions to fund (27) 27 (62) Retiree benefits paid (47) 47 84 (598) (298) 300 60 Ending balance What was the prior service cost at the beginning of the year? Multiple Choice $52 million. $60 million. $64 million. $68 million