trading well below takeover offer

MRZ is currently trading around 0.47.
MGR have offered $0.50 per MRZ security plus 1 merged Mirvac security for every 3 MGR held in excess of 20000 or 1 merged security for every 3 MRZ units. They will also pay 1cent div.

As I see it,if the takeover is successful (which is close to certain, unless there is a superior offer;if you purchase 20000 units at this price, you are guaranteed a 4cent per unit profit (i.e.close to 8%). Alternatively you can accept a 1 for 3 scrip offer. The deal will be completed by early December.

Am I missing something?