Cambridge Electronic Industries Plc’s bid for the environmental control company Tace Plc has excited the interest of two rival suitors: the highest offer has come from Massachusetts-based environmental group Thermo Electron with a cash offer of 255 pence per share, while Stac Inc, a buyout team from one of Tace’s US subsidiaries has made an offer of 252 pence per share; the Cambridge five-for-four share offer is currently worth 190 pence per share – Stac is free to raise its bid, an option that Cambridge says that it’s considering.