I was long 10 x CGC Sep 20 $25.50 Puts; the price was bouncing above/below $25.50 as markets closed and there was activity just after close around that level...so I was sitting there at 4:05pm unsure of what price would be used to determine whether those Puts would be auto-exercised (by IB) or not. They ultimately were not, and indeed sources like Yahoo show yesterday's close as $25.56, but yesterday there were several sources -- I forget which, I looked at several -- appearing to show the closing price as $25.42, which would have meant auto-exercise, and thus being short like $25K CGC over the weekend, which I didn't really want. So I want to know whether there's anywhere I can go just after markets close on expiration-Friday where I can see what the 'official' close is going to be considered for option auto-exercise purposes. Is that something posted by OCC or some other body on Fridays? (Because knowing definitively whether they're going to be exercised would have let me take corresponding action, e.g. buying 1,000 CGC in after-hours trading, to avoid big short position Monday.)