Consider a long solid, rigid hexagonal prism like a common type of pencil. The mass of the prism is $M$ and is uniformly distributed. The length of each side of cross-sectional hexagon is $a$. The moment of inertia $I$ of the hexagonal prism about its central axis is $I=\frac { 5 }{ 12 } M{ a }^{ 2 }$ Find the moment of inertia $I$ of the hexagonal prism about an edge of the prism.

**Details and Assumptions**:

- $M=1 \text{ kg}$, $a=1 m$