You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Emily Baker here.

ASSISTANT: Baker, how can I assist you?

USER: I have planned to visit San Francisco for a business trip, so could you please help me to book a flight from DCA to SFO?

ASSISTANT: May I know your travelling dates please?

USER: My preferable dates are from 07/10 to 07/12. Make sure that flight should contain 1 connection with the price limit of 200. Can you please check for it?

ASSISTANT: Baker, sorry to say there are no flights with your requirements.

USER: Ok, thank you for the information.

ASSISTANT: Thank you for approaching us.