NEW YORK -- Zynga ( ZNGA), the social games maker, is laying off 18% of its staff, or 520 employees, and closing its New York, Los Angeles and Dallas offices. One of Zynga's designers tweeted that Zynga LA is being shut down with about 55 people being fired. Zynga is cutting the jobs to save as much as $80 million in costs. "The work force reduction will occur across all functions and is expected to be substantially complete by August 2013," the company noted in a press release on Monda. Zynga said it will take a pretax charge of $24 million to $26 million in the second quarter, and $2 million to $5 million in the third quarter. The San Francisco-based Zynga has had a rough go of it in recent months, struggling to earn a profit on the shift to mobile from desktop. Ba-Zynga: Social Gamer Tumbles Amid LayoffsGeneral Motors ( GM) is being added to the S&P 500 and S&P 100, while AIG ( AIG) is being added to the S&P 100. Automaker GM is replacing H. J. Heinz ( HNZ) in the S&P 100 and 500 indices on Thursday. Heinz is being acquired by 3G Capital and Berkshire Hathaway ( BRK.A). AIG, the giant insurer, is replacing Baker Hughes ( BHI) on the S&P 100. S&P Baker Hughes will remain in the S&P 500. Cramer Quick Take: Wait on Buying Auto StocksFedEx ( FDX) recently took a $100 million charge for retiring some of its aircraft and said it will record $74 million in additional charges in its next fiscal year because it is speeding up retirement of other planes. The shipping giant also raised its quarterly dividend to 15 cents a share from 14 cents. Dollar General ( DG) is forecast by analysts to report on Tuesday first-quarter profit of 71 cents a share on revenue of $4.24 billion. Mattress Firm Holding ( MFRM) is forecast to report first-quarter earnings of 36 cents a share on sales of $274.4 million. 5 Hated Earnings Stocks That Deserve Your Love -- Written by Joseph Woelfel >To contact the writer of this article, click here: Joseph Woelfel >To submit a news tip, send an email to: email@example.com.