Rand Al'Thor signs a check payable to Egwene AI'vere and gives it to Egwene. Rand leaves blank the amount, but he authorizes Egwene to fill it in for $6,000. Egwene, however, secretly fills it in for $10,000. She then negotiates the check to Tar Valon Bank, to whom she owes $10,000. If Tar Valon is a holder in due course, it can enforce the check for a) $0 b) $6,000 c) $10,000 d) $4,000