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

Sentence1: yes i am rich I need expensive Sentence2: Yes, I'm celebrating a special occasion, so money is no object. Is A and B an expensive, 4-star guesthouse? Sentence3: We have 19 trains that meet that criteria, where will you be departing from? Sentence4: Great. I'm glad I could be of help. Sentence5: Will you only need 1 ticket? The train will leave Cambridge at 15:36. Sentence6: Thank you for calling. Sentence7: Have a nice day. Sentence8: the travel time is 79 minutes. anything else today? Sentence9: I don't have a expensive guesthouse. Sentence10: No. Thanks. Sentence11: Yes please book TR6524 on tuesday leaving at 14:45 going to norwich from cambridge. Please confirm departure time. Thank you. Sentence12: Yes please, I'm looking for a guesthouse with free wifi. The area doesn't matter. Sentence13: There are a few available. I highly suggest the University Arms Hotel. Would you like to book a room? Sentence14: I found a result for A and B Guest House in east that has internet. Would you like more info? Sentence15: how about a hotel type instead? Sentence16: Yes, please book for 5 people, for 4 nights starting on friday. Sentence17: I just need the train travel time , please. Sentence18: Hello, I need to take a train to Norwich on Tuesday, can you please tell me what's available? Sentence19: Booking was successful the Reference number is : ECPE3KUV . Is there anything else I can assist you with? Sentence20: Train TR6524 would work for you. Would you like me to book you passage? Sentence21: cambridge and should leave after 14:45 Sentence22: A and B guesthouse is moderately priced. Could you like an expensive guesthouse instead? Question: Who has spoken the sentence 19? (A) User (B) System
Answer: (B) System