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: I have none listed like that,a different price range maybe? Sentence2: Booking was successful.Reference number is : AENEDXFY Sentence3: There are two options here. Would you prefer the south or the centre? Sentence4: sorry about that! why yes, there are 10 options for inexpensive hotels. Sentence5: Sounds good. 1 person, 4 nights and leaving from Wednesday. Sentence6: You are set, ref number is CPD3XEJI is there anything else I can help you with? Sentence7: What date and time for your reservation? Sentence8: Can you try the other restaurant? Sentence9: I am in the process of completing your reservation and nandos city centre. What day will you be dining? Sentence10: Thank you for using our service, and enjoy your time in Cambridge! Sentence11: Would you like me to make you a reservation at nandos city centre? Sentence12: Sure. Just give me the reference number once you do it Sentence13: No I think I bugged you enough! You have been great and fast too! Sentence14: I would suggest autumn house Sentence15: How many people for the restaurant? Sentence16: Make the reservation for wednesday and then give me the reference number Sentence17: Nandos is located both in the south and in the centre. Would you like me to make a reservation for you? Sentence18: The reservation should be at 13:00 Sentence19: I also need a restaurant, preferably one that serves portuguese food and is the same price point as my hotel. Sentence20: I would like to have a 4 star rating with free parking. Sentence21: I don't mind. Surprise me! Sentence22: I'm currently planning a visit to Cambridge and looking for a cheap place to stay. I don't need internet or any frills. Any good suggestions? Sentence23: There will be just me. Sentence24: Yes, that would be fantastic. Thank you very much. Sentence25: I am unable to book it right now. Sentence26: So, you are saying there are no cheap hotels in all of Cambridge? Can you maybe look one more time? Thanks! Question: Who has spoken the sentence 21? (A) User (B) System
Answer: (B) System