You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I'm Kevin Lee.

ASSISTANT: How can I aid you?

USER:  I am planning to travels from LAS to IAD for a business meeting, can you please help me with booking a flight ticket?

ASSISTANT: May I know your planning dates?

USER: Sure, my departure date is on 05/15 and the return date is on 05/17.

ASSISTANT: Give me a minute, let me check the details.

USER: Sure, make sure that the price limit should not exceed 200.

ASSISTANT: Sorry Kevin, I couldn't find any flights on your request.

USER: Ok, no problem. Thank you for checking.

ASSISTANT: You are welcome.