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>Two consecutive photographs were taken with a camera of focal length 200 mm mounted on an airplane flying at a height of 1500 m. The overlap was exactly 60% and the size of prints was 250 mm 250 mm. The flying height was same in case of both the exposures and the flight was balanced so that there was no drift. The ground was flat and was 250 m above the mean sea level. Determine the scale of the photograph and the length of the air base.<image 1>
A. The scale of the photographs is 1 cm = 62.5 m;Air base = 625 m
B. The scale of the photographs is 1 cm = 68.5 m;Air base = 625 m
C. The scale of the photographs is 1 cm = 66.5 m;Air base = 625 m
D. The scale of the photographs is 1 cm = 64.5 m;Air base = 625 m

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
A
Two consecutive photographs were taken with a camera of focal length 200 mm mounted on an airplane flying at a height of 1500 m. The overlap was exactly 60% and the size of prints was 250 mm 250 mm. The flying height was same in case of both the exposures and the flight was balanced so that there was no drift. The ground was flat and was 250 m above the mean sea level. Determine the scale of the photograph and the length of the air base.<image 1>
A. The scale of the photographs is 1 cm = 62.5 m;Air base = 625 m
B. The scale of the photographs is 1 cm = 68.5 m;Air base = 625 m
C. The scale of the photographs is 1 cm = 66.5 m;Air base = 625 m
D. The scale of the photographs is 1 cm = 64.5 m;Air base = 625 m

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