Railcar maker Greenbrier (GBX) is advancing after the company early this morning rejected a $20.00 per share bid from American Railcar Industries (ARII), which is controlled by activist investor Carl Icahn. The bid, which was announced by Icahn yesterday morning, "grossly undervalues" the company, Greenbrier stated. Meanwhile, in a note to investors earlier today, research firm DA Davidson wrote that it "suspects" that Icahn or another strategic buyer will make a higher bid for Greenbier. The firm continues to believe that Greenbrier's earnings will increase going forward and it maintained a $25 price target and Buy rating on the stock. In early afternoon trading, Greenbrier rose 36c, or 1.77%, to $20.73.