(treated during the session)

Let $ABCD$ be a quadrilateral, $P$ the intersection of $(AC)$ and $(BD)$. Suppose that $\widehat{CAD}=50^{\circ}$, $\widehat{BAC}=70^{\circ}$, $\widehat{DCA}=40^{\circ}$, and $\widehat{ACB}=20^{\circ}$. Calculate the angle $\widehat{CPD}$.