<|im_start|>system
You are a helpful assistant. You first think about the reasoning process in the mind and then provide the user with the answer. You should try to truely solve the question by yourself without cheating.  <|im_end|>
<|im_start|>user
 Pipe A fills a tank of capacity 950 liters at the rate of 40 liters a minute. Another pipe B fills the same tank at a certain rate. A pipe at the bottom of the tank drains the tank at the rate of 20 liters a minute. If pipe A is kept open for a minute and then closed, and pipe B is open for a minute and then closed, and then pipe C is open for a minute and then closed, and the cycle is repeated, the tank will be full in 57 minutes. What is the rate at which pipe B fills the tank? Show your work in <think> </think> tags. And return the final answer in <answer> </answer> tags.<|im_end|>
<|im_start|>assistant
Let me solve this step by step.
<think>
user
30
Pipe A fills a tank of capacity 950 liters at the rate of 40 liters a minute. Another pipe B fills the same tank at a certain rate. A pipe at the bottom of the tank drains the tank at the rate of 20 liters a minute. If pipe A is kept open for a minute and then closed, and pipe B is open for a minute and then closed, and then pipe C is open for a minute and then closed, and the cycle is repeated, the tank will be full in 57 minutes. What is the rate at which pipe B fills the tank?
test