For the years ended December 31 (In thousands, except per share data)	2013	2012	2011
Net sales
Product sales	$2,074,967	$1,710,759	$1,690,064
Service sales	435,804	386,957	326,678
Total net sales	2,510,771	2,097,716	2,016,742
Cost of sales
Cost of product sales	1,412,621	1,178,115	1,143,828
Cost of service sales	287,057	260,858	215,967
Total cost of sales	1,699,678	1,438,973	1,359,795
Gross profit	$811,093	$658,743	$656,947
Research and development expenses	(68,874)	(59,712)	(62,115)
Selling expenses	(153,336)	(125,201)	(119,438)
General and administrative expenses	(355,264)	(312,384)	(288,540)
Operating income	$233,619	$161,446	$186,854
Interest expense	(37,020)	(26,329)	(20,834)
Other income, net	1,354	245	862
Earnings before income taxes	$197,953	$135,362	$166,882
Provision for income taxes	(59,972)	(43,073)	(48,262)
Earnings from continuing operations	$137,981	$92,289	$118,620
Discontinued operations, net of taxes
Earnings from discontinued operations	—	$3,043	$7,769
Gain on divestiture	—	18,512	—
Earnings from discontinued operations	—	$21,555	$7,769
Net earnings	$137,981	$113,844	$126,389
Basic earnings per share:
Earnings from continuing operations	$2.94	$1.98	$2.56
Earnings from discontinued operations	—	0.46	0.17
Total	$2.94	$2.44	$2.73
Diluted earnings per share:
Earnings from continuing operations	$2.88	$1.95	$2.52
Earnings from discontinued operations	—	0.45	0.17
Total	$2.88	$2.40	$2.69
Dividends per share	$0.39	$0.35	$0.32
Weighted average shares outstanding:
Basic	46,991	46,743	46,372
Diluted	47,912	47,412	47,013