What will be the final cost of bailing out our banks?
Central Bank governor Patrick Honohan differed with Finance Minister Michael Noonan's optimistic forecast earlier this week which predicted that we would recoup all the cash pumped into the banks bar Anglo Irish and Irish Nationwide.
Yesterday, Prof Honohan put the bill at as much as €40bn, or €10bn more than Mr Noonan.
That's no piffling sum and would make a significant difference to the national debt.
We won't know for some time who is right because selling off assets and predicting a share price is not easy.
When pressed by Fianna Fáil's Michael McGrath on the discrepancy, the Central Bank governor said Mr Noonan was hoping for improved prices and was making an assumption about future returns. A less polite explanation would have been to say Mr Noonan has taken a wild guess. The truth is that we won't know for sometime how much the bank bailout will cost.