Spoked Wheel Moment

A circular wheel with eight spokes has a total mass $M$ , a radius $R$ , and a uniform linear mass density.

The moment of inertia with respect to an axis perpendicular to the wheel's plane and passing through the wheel's center can be expressed as:

$\large{MR^{2} \left(\dfrac{a + b\pi}{ab + b\pi}\right)},$

where $a$ and $b$ are coprime positive integers . Determine $a+b$ .