You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: My name is Kenneth Clark. I want to visit Denver Zoo with my family, could you help me in booking the ticket?

ASSISTANT: Sure, please tell me the airport codes?

USER: It's from DCA to DEN. The dates of travel are from 12/09 to 12/11.

ASSISTANT: Ok, there is a flight 1000 of Frontier airlines available for you. Shall I proceed?

USER: Please book the ticket.

ASSISTANT: Ok, your ticket is booked.

USER: Thank you for your help.

ASSISTANT: Thank you, have a great journey.