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

Sentence1: Thank you for such great customer service. I am set for now. Goodbye. Sentence2: Can you book it for me and get a reference number ? Sentence3: i did not have any in mind Sentence4: I would recommend the Dojo Noodle Bar. Their phone number is 01223363471. Would you like to reserve a table? Sentence5: There is one Korean restaurant in the centre of town. Sentence6: Whenever is fine, just for me. Sentence7: I am sorry but there are no Korean restaurants in the cheap price range. Would you like to try another type of food or price range? Sentence8: To brighten up your Monday I have you booked at dojo noodle bar. Sentence9: I would like a restaurant in the cheap price range Sentence10: How about one that serves Asian Oriental food? Could I have the phone number? Sentence11: Yes, I am happy to book you at Dojo. What time would you like to book and for how many people in the party? Sentence12: The park is free it's called cherry hinton water play would you like the address? Sentence13: No, but are there any cheap Korean restaurants? Sentence14: What is the entrance fee for the parks? Sentence15: Hello, are there any attractions on the eastside? Sentence16: You are most welcome and thank you for contacting the Cambridge TownInfo Centre. Take care! Sentence17: I can book you at 10:00 in the morning if you like. Is there a particular day of the week you had in mind? Sentence18: Yes, there's entertainment, museums, boats, swimming pools, parks, multiple sports. Would you like information on a particular attraction? Question: Who has spoken the sentence 15? (A) User (B) System
Answer: (B) System