A circuit which is used for charging a battery is shown in the adjacent figure. The battery B has emf $$6\,\mathrm{V}$$ and internal resistance of $$2\,\Omega$$. The charging battery A has an emf of $$9\,\mathrm{V}$$ and internal resistance of $$1\,\Omega$$. The voltage across the points P and Q

A

$$8\,\mathrm{V}$$

B

$$7\,\mathrm{V}$$

C

$$4\,\mathrm{V}$$

D

$$4.2\,\mathrm{V}$$