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><image 1>A transistor, which may be approximated as a hemispherical heat source of radius ro = 0.1 mm, is embedded in a large silicon substrate (k = 125 W/m$\cdot$  K) and dissipates heat at a rate q. All boundaries of the silicon are maintained at an ambient temperature of T$\infty$= 27C,except for the top surface, which is well insulated.evaluate the surface temperature of the heat source for q =4 W.
A. 340.93K
B. 350.93K
C. 360.93K

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
B
<image 1>A transistor, which may be approximated as a hemispherical heat source of radius ro = 0.1 mm, is embedded in a large silicon substrate (k = 125 W/m$\cdot$  K) and dissipates heat at a rate q. All boundaries of the silicon are maintained at an ambient temperature of T$\infty$= 27C,except for the top surface, which is well insulated.evaluate the surface temperature of the heat source for q =4 W.
A. 340.93K
B. 350.93K
C. 360.93K

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