Given the task definition and input, reply with output. In this task, you are given a conversation between a flight agent and the customer. You are given 4 options and you need to select the goal of the conversation. It is provided as part of customer's context, which has to be one of the following: `book`: Make a new reservation, `cancel`: Cancel an existing reservation, `no_flight`: No flight found for the customer's preference, `no_reservation`: No reservation / No change / No cancellation was made in the conversation, mostly enquiring details

customer: Hello. 
 agent: Hello, how can I help you today? 
 customer: I am Ryan Lopez. I am planning to book a ticket from IAD. Can you please book a ticket for me? 
 agent: Sure, kindly mention your travel dates? 
 customer: My travelling dates are 09/17 and return back on 09/19. 
 agent: May I know your source airport code? 
 customer: My destination airport code is PHX. 
 agent: There is a flight with your requirement, airline is Frontier with price 200 and single connection. Shall I proceed with booking? 
 customer: Yes, you can proceed the booking. 
 agent: Your booking is done and flight number is 1005. 
 customer: Thank you for your help. 
 agent: Thanks for reaching us, have a good day.
book