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

Sentence1: I need to find a train from ely to cambridge. Sentence2: I would like to leave on Monday. Sentence3: What day and time would you like to travel? Sentence4: When would you like to arrive in Cambridge on Monday? Sentence5: You're very welcome, I am so glad to have been of service! Have a wonderful day now, bye! Sentence6: Thanks for being so helpful! I appreciate your time. I'm all set now. Sentence7: I have booked 5 tickets for you on TR6645. Your reference number is SZYJ90EL . What else can I assist with? Sentence8: Yes for 5. All I would need is the reference number. Sentence9: I really just need to leave after 15:45. The arrival time doesn't really matter. Sentence10: should i book it for you? Question: Who has spoken the sentence 7? (A) User (B) System
Answer: (B) System