Any notice, demand or other communication which may or is required to be given under this Agreement must be in writing and must be: (a) personally delivered; (b) transmitted by United States postage prepaid mail, registered or certified mail, return receipt requested; (c) transmitted by reputable overnight courier service, such as Federal Express; or (d) transmitted by electronic mail to Purchaser and Seller as listed below. Notice to one Purchaser shall constitute notice to all Purchaser and notice to one Seller shall constitute notice to all Seller.