Fiscal
Fiscal
Fiscal
2019
2018
2017
(in millions)
(in millions)
(in millions)
Net sales
$  41
$  702
$  928
Cost of sales
50
602
653
Gross margin
(9)
100
275
Selling, general, and administrative expenses
11
48
50
Research, development, and engineering expenses
3
39
40
Restructuring and other charges (credits), net
3
30 (1)
(3)
Operating income (loss)
(26)
(17)
188
Non-operating income, net
—
—
22 (2)
Pre-tax income (loss) from discontinued operations
(26)
(17)
210
Pre-tax gain (loss) on sale of discontinued operations
(86)
(2)
3
Income tax (expense) benefit
10
—
(70)
Income (loss) from discontinued operations, net of income taxes
$  (102)
$  (19)
$  143
4 .
discontinued operations .
in fiscal 2019 we sold our subsea communications - “ subcom ” business for net cash proceeds of $ 297 million and incurred a pre-tax loss on sale of $ 86 million related primarily to the recognition of cumulative translation adjustment losses of $ 67 million and the guarantee liabilities discussed below .
the definitive agreement provided that if the purchaser sells the business within two years of the closing date we will be entitled to 20 % of the net proceeds of that future sale as defined in the agreement in excess of $ 325 million .
the sale of the subcom business which was previously included in our communications solutions segment represents our exit from the telecommunications market and was significant to our sales and profitability both to the communications solutions segment and to the consolidated company .
we concluded that the divestiture was a strategic shift that had a major effect on our operations and financial results .
as a result the subcom business met the held for sale and discontinued operations criteria and has been reported as such in all periods presented on our consolidated financial statements .
upon entering into the definitive agreement which we consider a level 2 observable input in the fair value hierarchy we assessed the carrying value of the subcom business and determined that it was in excess of its fair value .
in fiscal 2018 we recorded a pre-tax impairment charge of $ 19 million which was included in income -loss from discontinued operations on the consolidated statement of operations to write the carrying value of the business down to its estimated fair value less costs to sell .
in connection with the sale we contractually agreed to continue to honor performance guarantees and letters of credit related to the subcom business ’ projects that existed as of the date of sale .
these guarantees had a combined value of approximately $ 1 .
55 billion as of fiscal year end 2019 and are expected to expire at various dates through fiscal 2025 ; however the majority are expected to expire by fiscal year end 2020 .
at the time of sale we determined that the fair value of these guarantees was $ 12 million which we recognized by a charge to pre-tax loss on sale .
also under the terms of the definitive agreement we are required to issue up to $ 300 million of new performance guarantees subject to certain limitations for projects entered into by the subcom business following the sale for a period of up to three years .
at fiscal year end 2019 there were no such new performance guarantees outstanding .
we have contractual recourse against the subcom business if we are required to perform on any subcom guarantees ; however based on historical experience we do not anticipate having to perform .
the following table presents the summarized components of income -loss from discontinued operations net of income taxes for the subcom business and prior divestitures : .
-1 included a $ 19 million impairment charge recorded in connection with the sale of our subcom business .
-2 included a $ 19 million credit related to the subcom business ’ curtailment of a postretirement benefit plan .

Question: In which year was the amount of Cost of sales largest?
Answer: 2017