You are shown a conversation between a user and system. Identify who has spoken the indicated sentence based on the conversation.

Let me give you an example: Sentence1:i need a place to dine in the center thats expensive Sentence2: I have several options for you; do you prefer African, Asian, or British food? Sentence3: Any sort of food would be fine, as long as it is a bit expensive. Could I get the phone number for your recommendation?Question: Who has spoken the sentence 2? (A) User (B) System
The answer to this example can be: Answer: (A) User
Here is why: The sentence 1 is said by a user because the intent of it says that the information has to be gathered from the system

OK. solve this:
Sentence1: I have you booked on the TR0637 train. The total cost is 16.60 GBP, and the reference number is KQMHCZNL . IS there anything else that I can help you with? Sentence2: I want to leave after 08:45 please Sentence3: yes, i will book that Sentence4: We have a large amount of trains that day, is there a specific location? Sentence5: Tell me the arrival time of the 09:39 train please Sentence6: The first train to London Liverpool street is at 09:39 and arrives at 11:07 in Cambridge. Does this time work for you? or would you like later? Sentence7: Thank you for using the Cambridge TownInfo Centre. Goodbye! Sentence8: Sure. The 9:30 train leaves London Liverpool Street on Friday and arrives in Cambridge by 11:07. Would you like me to book that? Sentence9: No that is everything that I need. Thank you so much for your help. Sentence10: I'm sorry. There is no train leaving from london live to cambridge on friday by 8:45. Would you like to try a different day or time? Sentence11: what are the available options Sentence12: I want to go from london liverpool street to cambridge. Sentence13: What time would you like to leave? Sentence14: I apologize for the earlier confusion, we do have trains leaving every two hours starting at 09:39 until 01:07am. Which time works for you? Sentence15: Yes, please help me book a train on Saturday. Sentence16: Of course, how many tickets will you need? Sentence17: I just need one ticket please. Sentence18: Oh sorry, I wanted a train on Friday, not Saturday. Anything after 08:45 from london liverpool street. to cambridge. Question: Who has spoken the sentence 15? (A) User (B) System
Answer:
Answer: (B) System