GOod analysis, but do remember that post trading halt it is unlikely you would see similar prices to what you have been analysing. The share price would revalue upwards to make purchasing post merger shares more expensive, in other words the arbitrage would be whittled away. Unless you can somehow beat others too it, although that to me isn't a bankable strategy.
It's similar to looking at another stock such as SDL, the moment approvals go through the gap will not stay as it is now in the share price, but adjust close to the original $0.57 bid.
Remember the market can be volatile but is unlikely to miss a situation where there is a blatant outright arbitrage to be made such as this. Heck if it does then good. But I can bet that if you watch the prices post merger that loss calculated will whittle away in no time due to the increase in share price.
Just my two cents.
ADU Price at posting:
73.0¢ Sentiment: Hold Disclosure: Held