The ex-theoretical price is over since the day ARA announced and recorded the Rights entitlement. Based on the closing price of $1.42 per share on 11 Nov, the ex-theoretical price was $1.356. When the market opens the following announcement, ARA share price has been trading very close to this ex-theoretical price since then. In a typical Right exercise, the price of companies exercising the Rights tends to be weak.
But in anyway, let me answer your question assuming the closing price is $1.18. The formula for theoretical ex-Rights is:
(last done price x outstanding shares) + (no. of rights x rights price)
outstanding shares + no. of rights
Do you want to try again based on this new formula? :)