Stocks extended gains on Monday as Apple (AAPL) - Get Report boosted the Dow Jones Industrial Average and Nasdaq and led tech names higher.

The S&P 500 was up 0.73%, the Dow added 0.7%, and the Nasdaq gained 0.9%.

Warren Buffett's Berkshire Hathaway (BRK.A) - Get Report disclosed a stake in Apple worth nearly $900 million. Berkshire held 9.81 million Apple shares as of March 31, a holding worth $1.07 billion at the time. Apple rose 3%, recovering slightly from recent pressure following its first quarterly sales decline in more than a decade. Shares were on track for their best one-day gain in six weeks. 

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Berkshire also slightly increased its stake in IBM (IBM) - Get Report , reduced its stake in Walmart (WMT) - Get Report  and unloaded its stake in AT&T (T) - Get Report .

Tech stocks were among the best performers on Wall Street on Monday. Alibaba (BABA) - Get Report , Texas Instruments (TXN) - Get Report , and Intel (INTC) - Get Report were higher, while the TechnologySelect Sector SPDR ETF (XLK) - Get Report rose 0.9%.

Homebuilder sentiment held steady in May, unchanged for the fourth month in a row as housing sector growth continues. The National Association of Home Builders' index remained at 58. A reading above 50 indicates improvement. The steady read was as expected. 

Economic conditions in the New York region worsened in May. The Empire State index turned negative with a reading of 9 compared to a positive reading of 9.6 in April. Economists expected a positive reading of 5.8.

Worries over China's economy, the world's second largest, flared over the weekend after industrial output, retail and investment data each missed estimates. Industrial production in China last momth rose just 6%, slowing from 6.8% growth in March. Weaker auto sales dragged on overall retail sales which climbed 5.1% in April, more than half the pace in March. Private investment in fixed assets grew at its slowest pace since 2012.

Crude oil jumped above $47 a barrel on Monday after Goldman Sachs said the oil market had flipped to a deficit "much earlier than we expected." Analysts said the market likely corrected in May as sustained strong demand and sharply declining production fueled the deficit. The firm expects crude to reach $50 a barrel in the second half of the year. West Texas Intermediate crude oil was up 2.8% $47.49 a barrel on Monday.

Pfizer (PFE) - Get Report agreed to acquire Anacor Pharmaceuticals (ANAC) for $99.25 a share, or $5.2 billion in cash. Palo Alto, Calif.-based Anacor currently has its lead product candidate, a topical treatment for eczema named crisaborole, under Food and Drug Administration review. Pfizer expects the deal to close in the third quarter of this year. Anacor shares surged 54%.

Tribune Publishing (TPUB) surged more than 21% after Gannett (GCI) - Get Report increased its acquisition offer to $15 a share from $12.25. Tribune's board had rejected the initial offer. Gannett, owner of USA Today, said the increased offer "reflects additional analysis of certain information revealed in Tribune's financial statements."

J.C. Penney (JCP) - Get Report climbed 1% after Baird upgraded the stock to outperform from neutral. Analysts said a recent 30% pullback from March levels makes for an attractive valuation. The firm set a $12 price target. 

Canaccord analysts upgraded Nokia (NOK) - Get Report shares and initiated a hold rating on Microsoft (MSFT) - Get Report . The firm upgraded Nokia to buy from hold, citing a valuation call based on a $7 price target. Microsoft's new rating was also a valuation call based on a $55 price target.