. A partially completed pension spreadsheet showing the relationships among the elements that constitute Carney, Inc.s defined benefit pension plan follows. At the end of 2018, Carney revised its pension formula and incurred a prior service cost of $100 million. At the end of 2019, the pension formula was amended again, creating an additional prior service cost of $200 million. At the beginning of 2020, $400 million prior service cost was incurred. At the beginning of 2021, $300 million prior service cost was incurred. In 2018 - 2021, the actuarys discount rate remained 10%, and the average remaining service life of the active employee group remained 10 years. The expected rate of return on assets was 10% in 2019, and increased by 1% each year.

1. Fill in blanks in the 2019 pension spreadsheet.

2019 Pension spreadsheet ($ in millions)	(PBO)	Plan Assets	Prior Service CostAOCI	Net Loss (Gain) AOCI	Pension Expense	Cash	Net Pension (Liability) / Asset
Balance, Jan. 1, 2019	(25,000)	20,000	100	4,500			(5,000)
Service cost	(800)
Interest cost
Prior Service Cost
Expected return on assets
Adjust for: Gain (loss) on assets
Amortization of: "Prior service cost-AOCI"
Amortization of: "Net Loss (Gain)-AOCI"
Gain (Loss) on PBO	7000
Cash funding						(1,000)
Retiree benefits	950
Bal., Dec. 31, 2019		22,450	290	(3,100)	1,510