Bayer closed in the Frankfurt exchange at a 3.2% higher at €87.15. The price is still down since the deal was first reported on May 12 as some investors were concerned that Bayer will need to hike its bid and pay more than necessary. The St. Louis-based Monsanto did not find the bid financially adequate. Analysts feel that Bayer is likely to come back with a higher bid and feels that anything that is below $135 per share is challenging. With this, Monsanto’s shares rose 3.1% to $109.30. Until the late 1970s, Monsanto produced highly toxic polychlorinated biphenyls, known as PCBs. It was also among companies that manufactured the mixture of herbicides known as Agent Orange and used as a defoliant by the US in the Vietnam War.