In the event that final bills are not available or cannot be issued prior to Closing for any item being prorated under Section 6.1 , then Purchaser and Seller agree to allocate such items on a fair and equitable basis as soon as such bills are available; final adjustment is to be made as soon as reasonably possible after the Closing, but in any event prior to the date that is ninety (90) days after Closing. Payments in connection with the final adjustment shall be due within thirty (30) days of written notice.