Two batteries of emfs 6 V and 3 V and internal resistances 0 · 8 Ω and 0 · 2 Ω respectively are connected in series to an external resistance R, as…

Two batteries of emfs $\displaystyle 6$ V and $\displaystyle 3$ V and internal resistances $\displaystyle 0 \cdot 8 \Omega$ and $\displaystyle 0 \cdot 2 \Omega$ respectively are connected in series to an external resistance $\displaystyle R$, as shown in figure. Find the value of R so that the potential difference across the $\displaystyle 6$ V battery be zero.