The following incomplete (columns have missing amounts) pension spreadsheet is for Old Tucson Corporation (OTC).

($ in millions) debit (Credit)	PBO			Plan Assets				Prior Service Cost				Net (Gain) Loss				Pension Expense				Cash				Net Pension (Liability)/Asset
Beginning balance	(530	)											67
Service cost																	71
Interest cost
Expected return on assets																	(26	)
Gain/loss on assets													(2	)
Amortization of:
Prior service cost									(9	)
Net gain/ loss
Loss on PBO	(28	)											28
Contributions to fund																					(65	)
Retiree benefits paid	49				(49	)
Ending balance	(610	)			306				63				87												(304	)

What was the prior service cost at the beginning of the year?