Microsoft says to buy Greenfield for $486 mln

Shares of Greenfield Online Inc., which provides marketing companies with Internet surveys, rose sharply Tuesday after the company called a $17.50-per-share cash takeover offer from an undisclosed suitor superior to a previous bid from private investment firm Quadrangle Group LLC.

Greenfield shares rose $1.26, or 7.9 percent, to $17.24. In the past year, the stock has ranged from $10.25 to $17.44.

Greenfield said it plans to terminate a merger agreement made in June with Quadrangle, which would have given shareholders $15.50 per share. The proposed transaction was worth about $407.9 million based on the company's 26.3 million outstanding shares as of May 2.

According to the agreement, Quadrangle has three days to increase its offer, Greenfield said. Terminating the agreement would cost Greenfield $5 million.

The new offer is not contingent on financing, Greenfield said.