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

Sentence1: It is a museum. Sentence2: Great, thanks. You answered all my questions and were very helpful. Have a good day. Bye. Sentence3: Where will you be coming from? Sentence4: What is the postcode? Sentence5: The postcode is cb30aq. Can I help you with anything else today? Sentence6: Sure what type of attraction were you looking for? Sentence7: I need a train that goes to Norwich. Sentence8: I don't have a preference. You pick. Sentence9: That will work, can you book me seats for 7 and let me know the reference number? Sentence10: I will be leaving on Sunday Sentence11: the lynne strover gallery is located at 23 high street, fen ditton. their phone number is 01223295264. the admission is free. would you like help with something else? Sentence12: What type of attraction this? Sentence13: Great. On which day will you be traveling? Sentence14: Yes, there is one that departs at 5:36 and arrives at 6:55 will that work? Sentence15: Happy to be of help. Goodbye. Sentence16: I'm also looking for something to help kill some time on the west side of town. Do you have any recommendations? Sentence17: Booking was successful, the total fee is 98.56 GBP payable at the station . Reference number is : YGMYZLL2 . anything else i can help you with? Sentence18: I'll be leaving from cambridge. Is there a train that can get there before 17:15? Question: Who has spoken the sentence 15? (A) User (B) System
Answer: (B) System