Given the task definition and input, reply with output. You are shown a conversation between a user and system. Identify who has spoken the indicated sentence based on the conversation.

Sentence1: You're welcome. Goodbye. Sentence2: Hello, I'm looking for the museum of classical archaeology, could you tell me more about it? Sentence3: Yes, I'd like that. Thank you so much! Sentence4: No, you've been very helpful. Thank you. Bye. Sentence5: The postcode for the Museum of Classical Archaeology is cb39da. Is there anything else I can help you with? Sentence6: Certainly, the museum of classical archaeology is located at sidgwick avenue and has free entrance, phone 01223335153. Do you also need the postcode? Question: Who has spoken the sentence 4? (A) User (B) System
Answer: (A) User