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, I am Christine Carter. 
 agent: Hello, how may I serve you? 
 customer: I am planning to visit a Lincoln memorial at Washington, so can you book a ticket with a connecting flight? 
 agent: Sure, can you please share your journey points? 
 customer: My journey airport codes are from CA-LAX to DC-IAD. 
 agent: May I know your travel dates? 
 customer: My travel dates are 09/08 and 09/10. 
 agent: Do you have any price limit? 
 customer: My price limit is 200. 
 agent: Please wait for a while. 
 customer: Ok. 
 agent: We found a UA airline with flight number 1019. Single connection and fare is 100. 
 customer: You can proceed. 
 agent: Your booking has been done. 
 customer: Thank you for your service. 
 agent: Thank you for choosing us.
book