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. Thank you for calling. Have a nice day. Sentence2: The Alpha-Milton guesthouse in the north and moderately priced. Would you like to book a room? Sentence3: The postcode is cb41xa. Can I help with anything else? Sentence4: No, thanks. That's all I needed. Have a great day. Bye! Sentence5: I'm looking to get some information on the alpha-milton guest house Sentence6: Not yet, but can you tell me the postcode for this guesthouse? Question: Who has spoken the sentence 4? (A) User (B) System
Answer: (A) User