A bid would have to be north of $5.00

There is no way the board of Vocus could approve a takeover bid that was only a premium to the current share price (it would be deemed too opportunistic by the market). To have a realistic chance of being accepted it would have to be at a reasonable premium to the average share price of the last few months. Therefore given the trading history this year, it suggests a takeover price would have to be north of A$5.00.