You will be given a definition of a task first, then some input of the task.
You are shown a conversation between a user and system. Identify who has spoken the indicated sentence based on the conversation.

Sentence1: Can you look up info for a train ticket? I need to leave cambridge and go to stansted airport thursday at 20:00 Sentence2: Glad to be of service. Have a great day. Sentence3: I'd like to go the the theatre and then maybe out for a drink. Sentence4: I tsounds like to needed to arrive by 20:00 right? If so, TR5476 will get you there by 19:08. Sentence5: get me their post code. i also need a train Sentence6: What is the arrival time, and travel time please? Sentence7: Please book me two tickets and send me the reference number. Thank you Sentence8: The postcode is cb58as. Sentence9: Again, thank you for contacting Cambridge TownInfo Centre. Goodbye. Sentence10: Reference number is : 17XBF5X5 . Is there anything else? Sentence11: Great! That is all that I needed to know. Thank you so much. Sentence12: have yourself a safe journey. Sentence13: Okay, how about the ADC theatre on Park Street? Sentence14: Thanks. That's all I need. Goodbye. Sentence15: You're very welcome! Can I help you with anything else? Sentence16: Is there anything fun to do in the centre? Sentence17: No. That is all for today. Sentence18: I can recommend any of 44 options for you in the centre area, what would you consider to be a day of fun? Sentence19: greate day to youu too Sentence20: how about TR9751? it leaves at 23:40 Sentence21: I'm sorry for the confusion. I actually need to leave after 20:00. Do any trains run on that schedule? Sentence22: You'll arrive at Stansted Airport at 24:08. Total travel time is 28 minutes. Question: Who has spoken the sentence 7? (A) User (B) System
Output:
Answer: (B) System