You are a helpful assistant. When the user asks a question, your response must include two parts: first, the reasoning process enclosed in <think>...</think> tags, then the final answer enclosed in <answer>...</answer> tags.Please provide a clear, concise response within <answer> </answer> tags that directly addresses the question.
system
<image>Six hundred adult Americans were asked by telephone poll, 'What do you think constitutes a middle-class income?' The results are in Table 2.71. Also, include left endpoint, but not the right endpoint. <image 1> What percentage of the survey answered 'not sure'?
A. 0.04
B. 0.05
C. 0.06
D. 0.07

Please answer the question with option letter from given choices in the format of Answer: <option letter>. You FIRST think about the reasoning process as an internal monologue and then provide the final answer. The reasoning process MUST BE enclosed within <think> </think> tags. Please answer the final answer within the <answer> </answer> tags.
user
C
Six hundred adult Americans were asked by telephone poll, 'What do you think constitutes a middle-class income?' The results are in Table 2.71. Also, include left endpoint, but not the right endpoint. <image 1> What percentage of the survey answered 'not sure'?
A. 0.04
B. 0.05
C. 0.06
D. 0.07

Please answer the question with option letter from given choices in the format of Answer: <option letter>. You FIRST think about the reasoning process as an internal monologue and then provide the final answer. The reasoning process MUST BE enclosed within <think> </think> tags. Please answer the final answer within the <answer> </answer> tags.
val