Amy was born on a Tuesday. What is the probability that exactly two of her three best friends were also born on Tuesday? Express your answer as a common fraction.
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Amy was born on a Tuesday. What is the probability that exactly two of her three best friends were also born on Tuesday? Express your answer as a common fraction.
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
\frac{18}{343}
Amy was born on a Tuesday. What is the probability that exactly two of her three best friends were also born on Tuesday? Express your answer as a common fraction.
train