I'm travelling sans laptop to plug it in to my model but it's...

I'm travelling sans laptop to plug it in to my model but it's pretty close to 30% post tax NPV uplift going from 13 to 20 years.

With prices where they are right now I think a sliding price assumption is best.  I think anyone producing in 21/22 will get a full 12 months of super pricing until inventories rebalance before a fall to long term average which $13 seems to be a fair proxy for.  Won't play out exactly that way but averages work out over time. 

A year of $20 pricing will bolt >$150 on to NPV, slash payback period and set the balance sheet up for expansion if conditions warrant. 

Does the 16th count as mid to late October?