(12) $0<b \leqslant 1$ Hint: By graphing, it can be known that the range of the real number $b$ is $0<$ $b \leqslant 1$.
(12) The line $y=b$ intersects the graph of the function $y=|x^2-4x+3|$ at least at three points, then the range of the real number $b$ is