For all changes and additions to the scope which the Buyer may request, in case there is any price impact, the Seller shall promptly submit a quotation indicating price with validity period, and shall indicate what (if any) effect this change may have to the project schedule. The Buyer, should it accept the requested quotation for the change, shall as soon as possible issue a formal Change Order. Failure on the part of the Seller to follow this procedure shall result in the rejection of requests for payment for changes for which no written authorisation has been received from the Buyer.