Iranian Mathematical Olympiad

Let $C$ be a circle and $P$ a point outside of it. $PA$ and $PB$ are the two tangent lines to this circle and point $K$ is chosen arbitrarily on the segment $AB$. The circumcircle of triangle $PBK$ intersects circle $C$ for the second time at $T$. Let $P^{\prime }$ be the reflection of $P$ with respect to $A$. Show that $\angle PBT=\angle P^{\prime }KA$.