\textbf{132-} Triangle $ABC$ is isosceles with $AB = AC$. Point $P$ is on face $P$ and point $M$ is outside face $P$, such that $MB = MC$ and $MA \perp AB$. Which of the following conclusions is \underline{incorrect}?
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(1) $MB \perp BC$ \hfill (2) $MA \perp AC$ \hfill (3) $MA \perp P$ \hfill (4) $MA \perp BC$
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