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>A gas-turbine power plant operates on the simple Brayton cycle between the pressure limits of 100 and 1600 kPa.The working fluid is air, which enters the compressor at 40°C at a rate of 850 m^3/min and leaves the turbine at 650°C. Using variable specific heats for air and assuming a compressor isentropic efficiency of 85 percent and a turbine isentropic efficiency of 88 percent, determine (1) the net power output and (2) the back work ratio.<image 1>
A. (1) 6001 kW, (2) 0.436
B. (1) 6181 kW, (2) 0.536
C. (1) 6081 kW, (2) 0.536

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
A gas-turbine power plant operates on the simple Brayton cycle between the pressure limits of 100 and 1600 kPa.The working fluid is air, which enters the compressor at 40°C at a rate of 850 m^3/min and leaves the turbine at 650°C. Using variable specific heats for air and assuming a compressor isentropic efficiency of 85 percent and a turbine isentropic efficiency of 88 percent, determine (1) the net power output and (2) the back work ratio.<image 1>
A. (1) 6001 kW, (2) 0.436
B. (1) 6181 kW, (2) 0.536
C. (1) 6081 kW, (2) 0.536

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