We sponsor programs that provide retirement benefits to most of our employees. These programs include defined benefit pension plans, defined contribution plans and postretirement healthcare plans. Key terms of our retirement plans are provided in our Annual Report. Our retirement plans costs for the three-month periods ended August 31 were as follows (in millions):

	2015		2014
Defined benefit pension plans	$	53	$	(7)
Defined contribution plans		102		94
Postretirement healthcare plans		21		20
	$	176	$	107

Net periodic benefit cost of the pension and postretirement healthcare plans for the three-month periods ended August 31 included the following components (in millions):

	Pension Plans				Postretirement Healthcare Plans
	2015		2014		2015		2014
Service cost	$	166	$	164	$	10	$	10
Interest cost		295		275		11		10
Expected return on plan assets		(377)		(420)		-		-
Amortization of prior service credit		(31)		(26)		-		-
	$	53	$	(7)	$	21	$	20

Contributions to our tax qualified U.S. domestic pension plans (“U.S. Pension Plans”) for the three-month periods ended August 31 were as follows (in millions):

	2015		2014
Required	$	6	$	82
Voluntary		159		83
	$	165	$	165

In September 2015, we made an additional required contribution of $165 million to our U.S. Pension Plans. Our U.S. Pension Plans have ample funds to meet expected benefit payments.