Rectangle A B C D has side lengths A B=84 and A D=42. Point M is the midpoint of \overline{A D}, point N is the trisection point of \overline{A B} closer to A, and point O is the intersection of \overline{C M} and \overline{D N}. Point P lies on the quadrilateral B C O N, and \overline{B P} bisects the area of B C O N. Find the area of \triangle C D P.