4. Let $A B C$ be an acute triangle, $\mathcal{K}$ a circle with diameter $A B$, $E$ and $F$ the intersections of the circle with sides $A C$ and $B C$, and $P$ the intersection of the tangents to the circle $\mathcal{K}$ at points $E$ and $F$. Calculate the ratio of the radii of the circumcircles of triangles $A B C$ and $E F P$.