Circles C1 and C2 intersect at A and B. Let M∈AB. A line through M (different from AB) cuts circles C1 and C2 at Z,D,E,C respectively such that D,E∈ZC. Perpendiculars at B to the lines EB,ZB and AD respectively cut circle C2 in F,K and N. Prove that KF\equal{}NC. geometry proposedgeometry