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 pipe of radius R has a fully developed laminarflow of air at P0, T0 with a velocity profile of V = Vc[1 - (r/R)2], where Vc is the velocity on the center-line and r is the radius, as shown in <image 1>. Find the total mass flow rate and the average velocity, both as functions of Vc and R.
A. $\begin{aligned}V&=\frac{V_c}{3}\\\dot{m}&=\frac{\pi}{2\cdot\nu}\cdot V_c\cdot R^2\\\\\end{aligned}$
B. $\begin{aligned}V&=\frac{V_c}{2}\\\dot{m}&=\frac{\pi}{2\cdot\nu}\cdot V_c\cdot R^2\\\\\end{aligned}$
C. $\begin{aligned}V&=\frac{V_c}{2}\\\dot{m}&=\frac{\pi}{2\cdot\nu}\cdot V_c\cdot R^3\\\\\end{aligned}$

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
A pipe of radius R has a fully developed laminarflow of air at P0, T0 with a velocity profile of V = Vc[1 - (r/R)2], where Vc is the velocity on the center-line and r is the radius, as shown in <image 1>. Find the total mass flow rate and the average velocity, both as functions of Vc and R.
A. $\begin{aligned}V&=\frac{V_c}{3}\\\dot{m}&=\frac{\pi}{2\cdot\nu}\cdot V_c\cdot R^2\\\\\end{aligned}$
B. $\begin{aligned}V&=\frac{V_c}{2}\\\dot{m}&=\frac{\pi}{2\cdot\nu}\cdot V_c\cdot R^2\\\\\end{aligned}$
C. $\begin{aligned}V&=\frac{V_c}{2}\\\dot{m}&=\frac{\pi}{2\cdot\nu}\cdot V_c\cdot R^3\\\\\end{aligned}$

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