Path of a Midpoint Between Two Equilateral Triangles

Given $AB = 10$, point $M$ is a moving point on segment $AB$. On the same side of $AB$, equilateral triangles $ACM$ and $MDB$ are constructed on $AM$ and $MB$ respectively. Connect $CD$ and let $N$ be the midpoint of $CD$. As $M$ moves from $A$ to $B$, describe how the distance from $N$ to line $AB$ changes, and find the length of the path traced by $N$.