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: I need a theatre in the centre of town. Sentence2: Sure, I also need a train that leaves from Cambridge and arrives by 16:45. Sentence3: Yes please book that for 2 people. Sentence4: The postcode is cb58as. Unfortunately, the entrance fee is unknown. Would you like the phone number so you can call them to ask? Sentence5: Sure, your reference number is LGM5AGUR . Is there anything else I can do for you? Sentence6: Of course, have a great day. Sentence7: Well, I need to arrive by 16:45, and want to depart from Cambridge. Does that one match my request? Sentence8: I found one that leaves at 05:21 would that work for you? Sentence9: Yes it does, it's train TR2025 if you'd like to book. Sentence10: No, I think that covers it all, thanks for your help. Sentence11: I would like to travel to Leicester on Sunday. Can you arrange this trip? Sentence12: I found four theaters. Would you like to try the ADC Theatre? Sentence13: That sounds good, I need the postcode and the entrance fee as well please. Sentence14: Adc theatre's phone is 01223300085. There are 819 trains departing cambridge. Could you be more specific on your destination and what day you'd like to leave on? Question: Who has spoken the sentence 4? (A) User (B) System
Answer: (A) User