Two identical rings each of mass `m` with their planes mutually perpendicular, radius `R` are welded at their point of contact `O`. If the system is free to rotate about an axis passing through the point `P` perpendicular to the plane of the paper, then the moment of in inertia of the system about this axis is equal to
A. `6.5mR^(2)`
B. `12mR^(2)`
C. `6mR^(2)`
D. `11.5mR^(2)`