Given the following user prompt and conversation log, formulate a question that would be the most relevant to provide the user with an answer from a knowledge base.
  You should follow the following rules when generating and answer:
  - Always prioritize the user prompt over the conversation log.
  - Ignore any conversation log that is not directly related to the user prompt.
  - Only attempt to answer if a question was posed.
  - The question should be a single sentence.
  - You should remove any punctuation from the question.
  - You should remove any words that are not relevant to the question.
  - If you are unable to formulate a question, respond with the same USER PROMPT you got.
  - The generated question must be in Chinese

conversation log= ‘
User: 一家四口，两大两小，买车有什么建议？
Agent: 
‘

user prompt= ‘推荐30万以内的’

Final answer: