Does anyone know, if I purchase a $100 item on hp.com, and have a $50 giftcard to use up, and pay the other $50 with my spg Amex, will it be considered a Amex purchase, and I will have Amex's extended warranty on the item, (for the $50 that i used Amex), or does the entire item need to be Amex without any coupon codes or gift cards applied?