I was wonder how to calculate net operating asset in this balance sheet

Net sales	$29,904	$ 29,611	$ 226,662
Operating expenses
Cost of sales	15,685	15,693	13,831
Selling, general and administrative expenses	6,102	6,170	5,479
Research, development and related expenses	1,634	1,570	1,434
	--	--	--
Total operating expenses	23,421	23,433	20,744
Operating income	6,483	6,178	5,918
Interest expenses and income
Interest expense	171	186	201
Interest income	(39)	(39)	(38)
Total interest expense--net	132	147	163
Income before income taxes	6,351	6,031	5,755
Provision for income taxes	1,840	1,674	1,592
Net income including noncontrolling interest	$4,511	$4,357	$4,163
Less: Net income attributable to noncontrolling interest	67	74	78
Net income attributable to 3M	$ 4,444	$ 4,283	$ 4,085

Assets
Current Assets
Cash and cash equivalents	$ 2,883	$ 2,219
Marketable securities-current	1,648	1,461
Accounts receivable-net of allowances of $105 and $108	4,061	3,867
Inventories
Finished goods	1,754	1,536
Work in process	1,186	1,061
Raw materials and supplies	897	819
Total inventories	3,837	3,416
Other current assets	1,201	1,277
Total current assets	13,630	12,240
Marketable securities-noncurrent	1,162	896
Investments	163	155
Property, plant and equipment	22,525	21,166
Less: Accumulated depreciation	(14,147)	(13,500)
Property, plant and equipment-net	8,378	7,666
Goodwill	7,385	7,047
Intangible assets-net	1,925	1,916
Prepaid pension benefits	16	40
Other assets	1,217	1,656
Total assets	$ 33,876	$ 31,616
Liabilities
Current liabilities
Short-term borrowings and current portion of long-term debt	$ 1,085	$ 682
Accounts payable	1,762	1,643
Accrued payroll	701	676
Accrued income taxes	371	355
Other current liabilities	2,281	2,085
Total current liabilities	6,200	5,441
Long-term debt	4,916	4,484
Pension and postretirement benefits	3,086	3.972
Other liabilities	1,634	1,857
Total liabilities	$15,836	$15,754
Equity
3M Company shareholders' equity	$9	$9
Additional paid-in capital	4,044	3,767
Retained earnings	30,679	28,348
Treasury stock	(12,407)	(11,679)
Accumulated other comprehensive income (loss)	(4,750)	(5,025)
Total 3M Company shareholders' equity	17,575	15,420
Noncontrolling interest	465	442
Total equity	$18,040	$15,862
Total liabilities and equity	$33,876	$31,616