You are shown a conversation between a user and system. Identify who has spoken the indicated sentence based on the conversation.
Q: Sentence1: Please tell me their phone number and address Sentence2: Glad I could help. Sentence3: I want to arrive by 18:30. Sentence4: Wandlebury Country Park is located at Wandlebury Ring, Gog Magog Hills, Babraham and their phone number is 01223243830. Can I assist you further? Sentence5: Can you help me find a park in the south? Sentence6: I'm travelling from Ely to Cambridge on Tuesday and need help finding a train. Sentence7: There are two parks in the south. They are both free. I recommend wandlebury country park. Can I help with anything more today? Sentence8: Great! How many seats will you need? Sentence9: thank you and enjoy your stay in Cambridge! Sentence10: Just me please Sentence11: Your booking was successful, the total fee is 4.4GBP payable at the station. Reference number is : FCO2L8AN. May I assist with anything else? Sentence12: I have several options available is there a time you would like to depart? Sentence13: That is all I need today. Thank you for your help. Sentence14: I don't have a departure preference. Sentence15: We have trains running that route every two hours beginning at 5:35. Do you have a preferred departure or arrival time? Sentence16: Thanks again for all of your help Sentence17: Train ID TR6971 is 4.40 pounds Should I book it Sentence18: Yes, and please give me the ref. number. Question: Who has spoken the sentence 15? (A) User (B) System
A:
Answer: (B) System