Q: You are shown a conversation between a user and system. Identify who has spoken the indicated sentence based on the conversation.
Sentence1: Of course! Your confirmation number is : NA5IKOHZ . Can I assist you with anything else today? Sentence2: Okay, sorry about the wait. I have booked 8 tickets for train TR7324. It will leave 21:40 and costs 600.79 GBP. The reference number is 2I340EJN . Sentence3: Thank you so much! Sentence4: Great, thanks so much Sentence5: Okay, let me work on booking that and I will be back with you shortly. Sentence6: Yes please. And I need the reference number please. Sentence7: Yes please, 8 people for 5 nights starting thursday, and can I get the reference number? Sentence8: How many tickets will you need? Sentence9: Can you help me find a place to stay maybe a expensive guesthouse? Sentence10: Have a great day. Goodbye. Sentence11: I have no expensive guesthouse's. Would you like to try a hotel or a different price range? Sentence12: Well, I preferred a guesthouse but since there are none, can you see if there are any hotels with my other specifications staying the same? Sentence13: That's great! I need a train. It should leave after 20:45 from Birmingham New Street. Sentence14: I have three trains. Do you need to book some tickets? Sentence15: what day, monday or friday please? And how many tickets? And are you going to Cambridge? Sentence16: I will need eight tickets please. Sentence17: I am showing nothing matching your request. Did you want to try another search? Sentence18: I was really wanting a guesthouse in the east with an expensive price range and include free parking. Sentence19: Yes, I'm going to Cambridge and I need to leave on Thursday. Sentence20: express by holiday inn cambridge fits that description. can i book for you? Sentence21: rad that's all i need now Sentence22: I will work on booking this for you and be back with you shortly. Question: Who has spoken the sentence 13? (A) User (B) System
A:
Answer: (B) System