As I indicated in my initial remarks, there are a number of components, ultimately, of that price. There's the crude price of crude, there are taxes, and there are ultimately the refining and retail margins. So I guess to that extent, yes, refiners do have an impact and do have a role in the price.
Around the issue of setting the price, ultimately the wholesale price, the price that refiners get for their product, is determined in the context of a North American market, and that's done in a transparent way through trading and posting of rack prices.
As for the third element of your question, the cost of refining is relatively stable, but it does change over time. Probably the most significant change to refining costs is the costs imposed on refiners due to increasing environmental regulations. We've talked about the costs that industry incurred in terms of a $5 billion dollar investment to respond to the desulphurization of gasoline and diesel, and we have looked beyond that, potentially, to other costs imposed on refining through the imposition of more strict regimes in terms of air pollutants. So yes, refining costs are an element of that, but this goes all the way from the price of crude to the retail margins, and ultimately it's the decisions of retailers who set the price of what consumers pay at the pump.