Updated with further terms of the ConAgra/Ralcorp merger agreementNEW YORK ( TheStreet) -- ConAgra Foods ( CAG) said Tuesday it agreed to buy Ralcorp Holdings ( RAH) for $90 a share in cash, or about $5 billion. The purchase price is a 28.2% premium to Ralcorp's closing price Monday of $70.23. Ralcorp shares were soaring in premarket trading Tuesday, up 26.7% to $88.99. The total value of the deal, including assumed debt, is $6.8 billion. A combined ConAgra/Ralcorp will have annual sales of about $18 billion, the companies said in a statement Tuesday. -- 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.