Doubt: Sir in this question how is the distance of charge 3Q equal to 3R??? please explain Chapter: Electrostatic Potential and Capacitance - Subject: Physics - Course: NEET Course

Sir in this question how is the distance of charge 3Q equal to 3R??? please explain

Outer radius must be 3R, And 2R is the separation between spherical Shell's.

Sir 2R is the radius of outer sphere... and I m asking for V(b) due to 3Q charge... it should be V(b) = k(3Q)/2R... isn't it?