OMCPLP 2014 Problem 4

From a point $K$ of a circle, a chord $KA$ (arc $AK$ is greather than $90^{o}$ ) and a tangent $l$ are drawn. The line that passes through the center of the circle and that is perpendicular to the radius $OA$ , intersects $KA$ at $B$ and $l$ at $C$ . Show that $KC = BC$ .