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

Sentence1: Thanks, that's everything. Sentence2: Hi. Can you book me a taxi to the Ugly Duckling from Dojo Noodle Bar? Sentence3: The taxi needs to arrive by 19:30. Sentence4: Thank you for choosing us for your booking. Have a great day! Sentence5: What time would you like to leave, and what time do you want to arrive by? Sentence6: I have booked you a red volkswagen. The contact number is: 07820586917. Can I help you with anything else today? Question: Who has spoken the sentence 4? (A) User (B) System
Answer: (A) User