Stocks ended the day higher on Monday as a continuing rise in home sales, a surge in merger activity and declining oil prices helped boost investor confidence.

The Dow Jones Industrial Average rose 84.76, or 0.83 percent, to 10,242.47, while the broader Standard & Poor’s 500 index gained 9.98, or 0.87 percent, to 1,162.10. The Nasdaq Composite Index rose18.59, or 0.96 percent, to 1,950.78.

A barrel of light crude settled at $54.57, off 82 cents on the New York Mercantile Exchange, after earlier rising to $56 a barrel but then dropping in afternoon trading.

The market was assisted by a surprising report by the National Association of Realtors, who said home sales rose at an annual rate of 6.89 million units in March, above the February figure of 6.7 million units. Economists said the report countered signs that the overall economy was weakening.

Meanwhile, the announcement that Valero Energy Corp., a San Antonio-based refiner with refining and retail operations in California, would spend $6.9 billion to buy Premcor Inc. indicated that corporate America still was willing to make big deals. The combined company would be the biggest domestic refiner. Also, DoubleClick Inc., the online marketing company, announced it would be acquired by a private equity firm for $1.1 billion.

Among local movers, Ixia rose 20.34 percent, or $2.84, to $16.80 following the Calabasas Internet network testing company’s announcement last week of higher earnings and record revenues in the first quarter. The company reported net income of $9.3 million (14 cents per diluted share) for the quarter ended March 31, compared with $3 million (5 cents) for the like period a year ago.

National Lampoon Inc rose 17.14 percent, or $0.60, to $4.10 after the Los Angeles-based entertainment company announced that its Web site, National Lampoon.com, has been named a Webby Award finalist in the Best Humor Site competition. The winners will be announced by the International Academy of Digital Arts and Sciences on May 3.