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: Hello. I am David Smith. 
 agent: Hello, How can I respond to your request? 
 customer: Can you please help me in booking a flight ticket from OAK to SFO? 
 agent: Sure, we are ecstatic to help you. On which dates would you like me to book a flight ticket for you? 
 customer: I would like to fly on Aug 21 and return on Aug 23. 
 agent: Would you like to travel in an economy class or in a business class? 
 customer: I am comfortable with any class. 
 agent: Please be on hold for sometime to check the suitable flight for your journey. 
 customer: Ok. 
 agent: We have found a connected flight with AA airlines, flight number 1004 and the fare of 100. Would you like me to book the ticket? 
 customer: You can proceed to booking. 
 agent: Your ticket has been confirmed. 
 customer: Thank you. 
 agent: Thanks for approaching us.
A:
book