2 disc of same moment of inertia rotating about their regular axis passing through the centre & perpendicular to the plane of disc with a1 &a2. they r bought face to face coincoiding to the axis of rotation . the loss of energy is

(A) I(a1-a2)2

(b) I/8(a1-a2)2

(c) I/2(a1+a2)2

(d) I/4(A1-A2)2