Given the task definition and input, reply with output. In this task, you're given a dialogue between a customer and a flight booking agent with a gap in the conversation. Your job is to find the answer of the previous dialogue. Avoid using irrelevant extra information while creating the answer. The answer should be relevant to the question before the blank. If you fill the blank with a question, it should have an answer from the agent in the given dialogue. Fill the gap marked with underline.

customer: Hi, I'm Margaret Taylor.
agent: Hello. How may I guide you?
customer: I am searching a flight, which travel towards IAD.
agent: Ok.
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agent: Sure, I would be happy to help you. May I know your preferable dates?
customer: My preferable dates are 09/18 and 09/20.
agent: I need your source code to proceed the booking, can you provide me?
customer: I would like to start my journey from my location, i.e MSP. Please check.
agent: Sure, I will check it.
customer: Ok.
agent: Give me a minute. I am sorry to say that there is no flight with your details.
customer: Oh! ok. Thank you for your help.
agent: Thank you for reaching us.
customer: Can you help me in booking a flight? Price limit is 500.