The correct option is B 4E7
Total resistance of circuit is Rt=R+2R.4R2R+4R=7R3
Current in the circuit is I=ERt=3E/7R
Potential across R is V1=IR=3E/7
As R and (2R, 4R) are in series so potential across (2R,4R) is V2=E−V1=E−3E/7=4E/7. This is also potential across 2R because 2R and 4R are in parallel.