M: Hi. This s the Customer Service. Can I help you? W: Hi. I bought one of your hair-dryers from Wal-Mart. But it's broken now. M: Ok. If you want to repair it, you may come to the service centre from Monday to Friday. If you want to change for a new one, please come to the service centre on Saturday. 19. When can the woman change for her hair-dryer?