Given the task definition and input, reply with output. You are shown a conversation between a user and system. Identify who has spoken the indicated sentence based on the conversation.

Sentence1: Yes, after 8:30 would be best. Sentence2: I have booked you a train ride on TR6488 which will depart at 09:21 and will arrive at 10:10. The total fee will be 10:24GBP. Would you like the reference number? Sentence3: No thank you. Thanks for your help. Sentence4: Great, thank you. That's all I needed. Sentence5: What is the total travel time? Sentence6: The post code is cb21ab and the phone number is 01223323737. Where would you like to book a train to? Sentence7: Where are you departing from? Sentence8: I would like the post code and phone number for the restaurant please, and I would like to book a train. Sentence9: The total travel time will be 49 minutes. Sentence10: You're welcome. Is there anything else I can do for you today? Sentence11: I'm leaving from Cambridge. Sentence12: I think something cheap. If not, go up to moderate. Sentence13: Do you have a time in mind? Sentence14: Good day to you. Sentence15: I suggest pizza hut city centre, it has a cheap price range. Would you like me to book it or would you like more information? Sentence16: Yes, Please book the reservation. Sentence17: I need to go to Stevenage on Sunday. Sentence18: I'd be happy to book a table for you. Please let me know the day, time, and the number of people in your party. Sentence19: There are nine of them. What price range do you prefer? Sentence20: I am looking for an Italian restaurant located in the centre of Cambridge. Question: Who has spoken the sentence 15? (A) User (B) System
Answer: (B) System