US stock market opens mixed on Wall Street; Family Dollar and Trulia jump on merger news

The stock market is opening mixed at the start of a busy week as a batch of merger announcements lift shares in Family Dollar and other companies.

The Dow Jones industrial average rose six points to 16,964 shortly after the market opened Monday. The Standard & Poor's 500 index eased three points to 1,976. The Nasdaq composite gained two points to 4,451.

Family Dollar soared 23 percent after Dollar Tree announced plans to buy the rival discount store. Meanwhile, Trulia jumped 11 percent after the real-estate listing service Zillow said it plans to buy it for $3.5 billion.

With one of trading week left in July, the stock market was on track for another month of solid gains.