In \triangle A B C, A B=13, A C=5 and B C=12. Points M and N lie on \overline{A C} and \overline{B C}, respectively, with C M=C N=4. Points J and K are on \overline{A B} so that \overline{M J} and \overline{N K} are perpendicular to \overline{A B}. What is the area of pentagon C M J K N ?
Answer Choices
A. 15
B. \dfrac{81}{5}
C. \dfrac{205}{12}
D. \dfrac{240}{13}
E. 20