6.	Inventories

We value our raw materials, work in process, and finished goods inventories using lower of cost, as determined by the average cost method, or market. Supplies and materials are valued at the first-in, first-out (FIFO) or average cost methods.

The components of inventories were as follows (dollars in millions):

	June 30,		December 31,
	2017		2016
Raw materials	$	257.6	$	271.9
Work in process		13.6		12.9
Finished goods		222.4		206.5
Supplies and materials		240.8		232.3
Inventories	$	734.4	$	723.6