Detailed Instructions: 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
Q: customer: Hi. Donna Evans here. 
 agent: Hello, how can I help you today? 
 customer: I would like to prefer a flight with lay-by option for my business trip to Oakland. Can you book a flight ticket? 
 agent: Sure, let me know your travel dates please? 
 customer: The trip dates are from 01 Feb to 03 Feb. 
 agent: Can I know your airport codes? 
 customer: The airport codes are from PHL to OAK. 
 agent: Any preferences you have? 
 customer: No, that is it. 
 agent: Spirit Airlines has a connecting flight with number 1018 for fare 200, shall I proceed? 
 customer: I am fine with the airlines. You can book the flight ticket. 
 agent: Your ticket is reserved in economy class. 
 customer: Thank you. 
 agent: Thank you for opting us.
A:
book