Here's a quick look at the numbers:
US$81: The U.S. benchmark price for a barrel of oil when the federal government released its fall economic update.
US$46: The price of oil in recent days.
$4.9 billion: The surplus forecast by the government's fall economic update, including a $3-billion contingency reserve, for 2015-16.
$400 million: The deficit the PBO expects for the 2015-16 fiscal year if the price of oil averages US$48 per barrel.
$700 million: The surplus the PBO expects for the 2015-16 fiscal year if the price of oil averages US$51 in 2015 and US$60 in 2016.