5.2.4.18 Various problems on the plane

In a convex quadrilateral \( A B C D \) the diagonals intersect at the point \( M \), and \( C M=D M \). Find the angle between the straight line \( C D \) and the bisector of the angle \( B A C \), if the angle \( A B M=78^{\circ} \) is known.