An massless equilateral triangle EFG of side 'a' (As shown in figure) has three particles of mass $m$ situated at its vertices. The moment of inertia of the system about the line EX perpendicular to EG in the plane of EFG is $\frac{N}{20} m a^2$ where $N$ is an integer. The value of $N$ is $\_\_\_\_$ .