Work done, W=21​Iω2If x is the distance of mass 0.3 kg from the centre of mass, we will have,I=(0.3)x2+(0.7)(1.4−x)2For work to be minimum, the moment of inertia (I) should be minimum,dxdI​=02(0.3x)−2(0.7)(1.4−x)=0(0.3)x=(0.7)(1.4−x)x=0.3+0.7(0.7)(1.4)​=0.98 m​Alternate method : I is minimum about an axis passing through centre of mass. So, find position of centre of mass.