A 6 volt battery of internal resistance $1\mathrm{\Omega }$ is connected across a uniform wire AB of length 100 cm.The positive terminal of another battery of emf 4V and internal resistance $1\mathrm{\Omega }$ is joined to the point A as shown. Find the distance of point D from A if potential of C is equal to potential of D.(resistance of $\mathrm{AB}=5\mathrm{\Omega }$ )