Instructions: You are shown a conversation between a user and system. Identify who has spoken the indicated sentence based on the conversation.
Input: Sentence1: Can you book it for me and get a reference number ? Sentence2: Train TR1526 leaves 17:40 and will get you there by 18:08. Would you like some tickets? Sentence3: Yes, that would be great. I'll need tickets for 7 people. I'll also need the reference number. Sentence4: I'm going from Cambridge to Standsted airport. Sentence5: Where are you departing from and what is your destination ? Sentence6: Can you help me find a train leaving on sunday and arriving by 18:15? Question: Who has spoken the sentence 4? (A) User (B) System
Output:
Answer: (A) User