Two wheels A and B of moment of inertia I and 3 I respectively

Two wheels A and B of moment of inertia I and 3 I respectively are spinning in the opposite direction side by side about a same axis with speed 400 r.p.m. and 200 r.p.m. respectively. A clutch now acts to join A and B so that they spin together. What is their Speed of rotation?

a) 50 r.p.m b) 100 r.p.m
c) 150 r.p.m d) 300 r.p.m