Within the creditCard field set, insert another field set containing four label elements, with each label element belonging to the cardLabel class. Within each of the four label elements, insert an option button from the cCard field with the value amex, discover, master, and visa. Make cCard a required field. Follow each option button with an image element containing the image of its corresponding credit card image using the sb_amex.png, sb_discover.png, sb_master.png, and sb_visa.png files.