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: No, that's all I needed. Thank you. Sentence2: Of course. When would you like to leave? Sentence3: I am looking for a train departing from london kings cross. Sentence4: Yes, please book the train for 4 people. Sentence5: Okay. Glad we could help. Sentence6: It does not matter as long as I am in Cambridge by 17:00. Sentence7: That booking reference will be F6JIDI3M . Is there anything else I can help you with today? Sentence8: Sure, train TR0269 arrives by 16:08. That is the last train to arrive by 17:00. Would you like to book it? Sentence9: I would like to arrive in Cambridge on Tuesday by 17:00. Sentence10: There are 70 trains departing, what is your destination? Question: Who has spoken the sentence 4? (A) User (B) System
Output:
Answer: (A) User