Summarizing Documents Made Easy With Langchain Summarizer

hi, this is an amazing blog Thanks!. However i have a question, i'm not able to pass the prompt variable into load_summarize_chain. it says "extra fields not permitted (type=value_error.extra)"

Thanks for the valuable post. Would like to know more about how many OPENAI tokens are required to digest the PDF and also to summarize and ask Q&A with documents?. Do you have any statistics of this tokens and its associated cost?