5. Let $\triangle$ABC be a triangle with circumcentre O. The perpendicular line from O to BC intersects line BC at M and line AC at P, and the perpendicular line from O to AC intersects line AC at N and line BC at Q. Let D be the intersection point of lines PQ and MN. construct the parallelogram PCQJ with PJ || CQ and QJ || CP. Prove the following: a) The points A, B, O, P, Q, J are all on the same circle. b) line OD is perpendicular to line CJ.