In $△ABC$, $AB=10$, $AC=6$, and $BC=8$. Points $M$ and $N$ lie on $AC$ and $BC$, respectively, with $CM=CN=2$. Points $J$ and $K$ are on $AB$ so that $MJ$ and $NK$ are perpendicular to $AB$. What is the area of pentagon $CMJKN$? Refer to the diagram below.