Two identical rings of radii 0.1 m are placed co-axially at a distance 0.5 m a part. The charges on the rings are 2μC  and 4μC  respectively. The work done in transferring 5μC  charge from the centre of one ring to that of the other will nearest to

Q=5×10-6C R=0.1m x=0.5m q1=2×10-6C q2=4×10-6C Potentaial ata apoint on axis, V=kqx2+R2initial potential energy when a charge Q=5μC is placed at the centre of first ringU1=Qkq102+R2+kq2x2+R2Final potential energy when a charge Q=5μC is placed at centre of second ringU2=Qkq202+R2+kq1x2+R2work done =W=ΔU=U2-U1=Qkq202+R2+kq1x2+R2-Qkq102+R2+kq2x2+R2=0.75J