Seven years ago, Elise Damato started a business specializing in dog walking and dog grooming. After the first year, her pet food supplier started giving Elise a cash discount of 2.25% on any amount paid within 15 days of the invoice date. On October 25, Elise bought pet food costing $1,064. On November 8, Elise paid $800 on the purchase. Compute the unpaid balance. (This problem involves the partial payment of an invoice within the discount period.)