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		450	60	55			50
Service cost	(85)
Interest cost	(25)
Expected return on assets		55
Gain/loss on assets				3
Amortization of:
Prior service cost
Net gain/loss				(1)
Loss on PBO	(65)
Contributions to fund		40
Retiree benefits paid
Ending balance	(530)		54	122

What is the PBO at the beginning of the year? a. 160, b. 400, c. 500, d. 610