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: Myself Kevin Wright, I have a business meeting in Detroit. Can you please help me to book my ticket from AUS to DTW? 
 agent: Sure, can I know your preferred dates of travel? 
 customer: My planned dates are from 06/26 to 06/28. 
 agent: There is a flight available on your given dates, ticket price is 100 only. Shall I book the ticket? 
 customer: Sure, you can proceed for booking my ticket. 
 agent: Your ticket has been booked successfully with Delta airline and the flight number is 1020. 
 customer: Thank you for booking my ticket. 
 agent: Thank you for choosing us, have a safe journey. 
 customer: You are welcome.
book