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: Great. Thanks. Can you look up a restaurant for me? Sentence2: There are several trains that day, do you know what time you want to leave or arrive? Sentence3: Yeah, that sounds great. Sentence4: There is a train departing Cambridge at 15:21 and arriving in Cambridge at 17:06. Can I book that for you? Sentence5: Okay, I've booked you a seat on the 15:21 train on Tuesday. The total fee is 37.79 GBP payable at the station . Reference number is : NHFGUN35 . Sentence6: I want to go to Leicester and want to leave on Tuesday. Sentence7: What about the phone number? Sentence8: I need to get there by 17:15 Sentence9: Yes and their phone number is 01223363270. Sentence10: Thanks so much for your help. Sentence11: Hello, I'd like some information on a train departing from cambridge. Sentence12: 1. please also get me z restaurant called city stop restaurant.and give me phone number and postcode Sentence13: how many tickets would you like? Sentence14: Certainly. What is your destination and what day will you be leaving? Sentence15: Can you book it for me and get a reference number ? Sentence16: Sure, the address is Cambridge City Football Club Milton Road Chesterton cb41uy. And just to confirm, you wanted to book 1 ticket for that train? Question: Who has spoken the sentence 15? (A) User (B) System
Output:
Answer: (B) System