The following refers to the pension spreadsheet (columns have missing amounts) for the current year for Pancho Villa Enterprises (PVE). ($ in millions) Debit(Credit)PBO Plan Assets Prior Service Cost Net (Gain)/Loss Pension Expense Cash Net Pension (Liability)/ Asset Beginning balance 456 66 61 57 Service cost (91) Interest cost (31) Expected return on assets 61 Gain/loss on assets 3 Amortization of: Prior service cost Net gain/loss (2) Loss on PBO (71) Contributions to fund 46 Retiree benefits paid Ending balance (536) 58 128 What was the PBO at the beginning of the year