It's anyone's guess but often in these cases the shares trade at somewhere between the placement price and the pre-placement price. The idea is that if you take up your entitlement you should be neither richer nor poorer, whereas if you don't you would be poorer due to dilution. However, the price can be moved by market sentiment outside of the theoretical range theory suggests.
For example, say you have 1000 shares at $1 each. There is a 1:1 rights offer at $0.80 a share, so you fork out $800 for your full allotment. Before the issue you had 1000 shares worth $1000 and $800 in cash, a total of $1800; after the issue you have 2000 shares which should be worth the same amount, so the theoretical share price should be $0.90.
OSH Price at posting:
$6.75 Sentiment: LT Buy Disclosure: Held