and accounts payable are carried at cost, which approximates fair value. The estimated fair values of our long-term debt instruments at December 31, 2011 and 2010, aggregated approximately $7.8 billion and $6.2 billion, compared with a carrying amount of approximately $7.0 billion and $5.5 billion, which excludes $506 million and $505 million of unamortized discounts. The fair values were estimated based on quoted market prices of debt with terms and due dates similar to our long-term debt instruments. Note 16 – Summary of Quarterly Information (Unaudited) 2011 Quarters (In millions, except per share data) First (a) Second (a) Third Fourth Net sales (b) $10,626 $11,543 $12,119 $12,211 Operating profit 864 993 1,041 1,082 Net earnings from continuing operations (c) 556 748 665 698 Net earnings (loss) from discontinued operations (d) (26) (6) 35 (15) Net earnings 530 742 700 683 Basic earnings per share (e) 1.52 2.16 2.12 2.12 Diluted earnings per share (e) 1.50 2.14 2.10 2.09 2010 Quarters (In millions, except per share data) First (a) Second (a) Third Fourth Net sales (b) $10,308 $11,259 $11,343 $12,761 Operating profit 938 1,119 877 1,115 Net earnings from continuing operations (c) 519 717 557 821 Net earnings from discontinued operations (d) 14 107 3 140 Net earnings 533 824 560 961 Basic earnings per share (e) 1.43 2.24 1.56 2.70 Diluted earnings per share (e) 1.41 2.22 1.54 2.67 82 (e) The sum of the quarterly earnings per share amounts do not equal the earnings per share amount included on our Statements of Earnings, primarily due to the timing of our share repurchases during 2011 and 2010. (d) The third quarter of 2011 included a tax benefit of $66 million related to Savi and the second quarter of 2010 included a tax benefit of $96 million related to PAE, both of which were recorded when the decision was made to dispose of each business. The fourth quarter of 2010 included a gain of $184 million from the sale of EIG. See Note 14 for further information related to these items. (c) The second quarter of 2011 included a reduction in income tax expense of $89 million due to the resolution of certain tax matters (Note 8) and a charge of $97 million ($63 million after tax) related to severance actions (Note 2). The fourth quarter of 2011 included an increase of $107 million ($66 million after tax) in the non-cash FAS/CAS pension expense adjustment and a decrease in R&D tax credits of $36 million, each as compared to the fourth quarter of 2010, and included a premium of $46 million ($28 million after tax) on the early extinguishments of debt. The first quarter of 2010 included an increase in income tax expense of $96 million resulting from legislation that eliminated the tax deduction for benefit costs reimbursed under Medicare Part D (Note 8). The third quarter of 2010 included a charge of $178 million ($116 million after tax) related to the VESP (Note 2). The fourth quarter of 2010 included a charge of $42 million ($27 million after tax) related to facilities consolidation within our Electronic Systems business segment (Note 2). (b) The decrease in net sales from the fourth quarter of 2010 to the fourth quarter of 2011 is primarily due to declines in net sales at our Electronic Systems, IS&GS, and Space Systems business segments. The decline at Electronic Systems was primarily due to fewer deliveries on tactical missile programs and net declines in volume on various other programs. The decline at IS&GS was primarily due to lower volume due to the absence of the Decennial Response Integration System (DRIS) program that supported the 2010 U.S. census and a decline in activities on the Airborne Maritime Fixed Station Joint Tactical Radio System (JTRS). The decline at Space Systems was primarily due to decreased volume related to satellite activities. (a) Net sales, operating profit, and net earnings (loss) from continuing and discontinued operations varies from the amounts previously reported on Forms 10-Q as a result of Savi being classified as discontinued operations in the third quarter of 2011.