You will be given a definition of a task first, then some input of the task.
You are shown a conversation between a user and system. Identify who has spoken the indicated sentence based on the conversation.

Sentence1: Thank you. Please do not hestitate to call if require further assistance. Sentence2: I would like a hotel in the north please. Sentence3: Which one has nights available from Thursday to Tuesday? Sentence4: Sure, we have 2 hotels in the north, ashley hotel and lovell lodge. Would you like to book one? Sentence5: Your booking is successful. The total fee is 23.6 GBP and your booking reference number is DOS0ARZU . Sentence6: There's a train on Friday leaving at 17:00. Should I book it? Sentence7: There are 28 trains meeting that criteria. What day are you wanting to leave? Sentence8: I am looking for a 2 star hotel with free wifi. Sentence9: Looks like you are all set. Goodbye! Sentence10: There aren't any that match your criteria in the centre. Any other suggestions? Sentence11: I am looking for a hotel near the city center moderately priced. Sentence12: I'm not sure. I will need to attempt a booking to give you that information. Which would you like to book? Sentence13: Thank you! I also need a train from cambridge to london kings cross. I need to depart after 16:00. Sentence14: There are three hotel types available. Do you want a specific area or price range? Sentence15: You're all set! Your reference number is JUZ789Y1 . How else may I help you? Sentence16: Please book the Ashley hotel for 1 person for 5 nights starting on Thursday Sentence17: I need a train for 1 from Cambridge leaving after 16:00 heading to London Kings Cross. Can you find any trains for that time and send me a reference number? Sentence18: Yes, please. Just the one ticket. Sentence19: Is there a specific day that you want to travel? What time do you want to arrive by? Sentence20: Tuesday and I would like to leave after 16:00. Question: Who has spoken the sentence 18? (A) User (B) System
Output:
Answer: (A) User