Teck used NPV 8% when sanctioning QB2. They, like all mining companies, use conservative numbers for NPV and metal prices even at the FS stage. I don't see how CUU will be allowed to use anything other than what Teck approves. Another issue is where are the two NPI's applied in the revenue stream. Is one subordinate to the other? Is there a difference between a Net Profits and a Net Proceeds? I don't doubt it's complicated, particularly if the wording in the original agreements is not clear or ambiguous.  That's probably why they ignored this issue in the 2013 FS.