Question 52
The incircle of $\triangle ABC$ is tangent to the sides $AC$ and $BC$, $AC \neq BC$, at points $P$ and $Q$, respectively. The excircles to the sides $AC$ and $BC$ are tangent to the line $AB$ at points $M$ and $N$. Find $\measuredangle ACB$ if the points $M, N, P$ and $Q$ are concyclic.