Given the task definition and input, reply with output. You are shown a conversation between a user and system. Identify who has spoken the indicated sentence based on the conversation.

Sentence1: You're welcome. Good bye. Sentence2: Gourmet Burger Kitchen is a restaurant serving North American food and in the Expensive price range. The phone number is 01223 312598 and the address is Regent Street City Centre. Sentence3: I'd like to find a north american restaurant in any area. I'd like the address, phone, and price range. Sentence4: Thank you. Goodbye! Sentence5: Thank you, goodbye. Sentence6: Good bye. Question: Who has spoken the sentence 4? (A) User (B) System
Answer: (A) User