The short answer is basically that what we're saying is based on the work at Pembina Institute. To our mind, it's not the end of the world if we have a slower pace of tar sands development.
I just want to clarify one point about what we were saying earlier. It is my understanding that under Kyoto we are committed to do a combination of three things, not two things. One is to reduce our emissions. The second is that we can use the clean development mechanism. The third thing is that we can take on an additional obligation in the subsequent period. It's not just an either/or in terms of reductions or purchasing credits.