Wall Street opens slightly higher, Dow retakes 18,000 mark

Wall Street opened slightly higher on Tuesday, with the Dow rising above the 18,000 mark, as investors assess quarterly earnings and await the outcome of a two-day U.S. Federal Reserve meeting. A rise in oil prices and a 2 percent rise in Dupont helped the Dow Jones industrial average cross the key psychological barrier. Fed officials have repeatedly said a hike in June is on the cards.