If $$\begin{array}{@{}l@{\;}l@{}l@{}l} && & P_b \\ & \times & & P_b \\ \cline{2-4} & & 3 & 1_b, \\ \end{array} $$where $P$ and $b$ represent two distinct digits 0-9 and $P$ is one less than $b$, what is the value of the base $b$?
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
If $$\begin{array}{@{}l@{\;}l@{}l@{}l} && & P_b \\ & \times & & P_b \\ \cline{2-4} & & 3 & 1_b, \\ \end{array} $$where $P$ and $b$ represent two distinct digits 0-9 and $P$ is one less than $b$, what is the value of the base $b$?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
5
If $$\begin{array}{@{}l@{\;}l@{}l@{}l} && & P_b \\ & \times & & P_b \\ \cline{2-4} & & 3 & 1_b, \\ \end{array} $$where $P$ and $b$ represent two distinct digits 0-9 and $P$ is one less than $b$, what is the value of the base $b$?
train