Four identical solid spheres each of mass `M` and radius `R` are fixed at four corners of a light square frame of side length `4R` such that centres of spheres coincides with corners of square, moment of inertia of `4` spheres about an axis passing through any side of square is

Options

A. `(21MR^(2))/5`
B. `(42MR^(2))/5`
C. `(84 MR^(2))/5`
D. `(168 MR^(2))/5`

Answer

D

Explanation

`I=2(I_(c)+I_(1))` and `I_(1)=I_(c)+Md^(2)`
`I_(c)=2/5 MR^(2)` and `d=4R`