You will be given a definition of a task first, then some input of the task.
You are shown a conversation between a user and system. Identify who has spoken the indicated sentence based on the conversation.

Sentence1: Sorry. TR2052 departs from leicester and the destination is cambridge. It leaves at 15:09 on Wednesday. Would you like me to book it for you? Sentence2: Yes, I only need 1 ticket for myself. Sentence3: There are 13. I could recommend Trinity College on Trinity Street. Or would you like information about one of the others? Sentence4: I would like to arrive by 17:00 in leicester. Sentence5: I would like help finding a college to visit in the centre of town. Sentence6: Of course. The address is Trinity Street, postcode is CB21TQ, and the entrance fee is one pound. Can I help you with anything else? Sentence7: Yes and please give me the reference number. Sentence8: OK, I've booked one ticket for you on TR0451 from cambridge to leicester, arriving at 16:06. Ref# 8OZNJHMO . Can I help you with anything else today? Sentence9: That sounds good. Could you give me the entrance fee, phone number, and postcode? Sentence10: Certainly. Just to verify, are you traveling alone? You would only like one ticket? Sentence11: TR3702 LEAVES AT 05:00 CAN I BOOK THAT ONE FOR YOU? Sentence12: How early do you wish to arrive? There are 11 trains that will get you there before 17:00. Sentence13: Thank you for using our service. Have a good night. Goodbye. Sentence14: Does this train go to Leicester from Cambridge? Sentence15: Yes I'm also looking for a train that leaves wednesday and arrives by 17:00. Sentence16: I think that is all I need, thank you. Question: Who has spoken the sentence 4? (A) User (B) System
Output:
Answer: (A) User