AAI ATC Junior Executive 25 Mar 2021 Shift 2 Paper

Given an isolated conducting spherical shell of radius 30 cm. Some positive charge is given to it so that the resulting electric field has a maximum intensity of 1.8 × 10⁶ NC^-1 The same amount of negative charge is given to another isolated conducting spherical shell of radius 60 cm. Now, the first shell is placed inside the second so that both are concentric as given in the figure below. Find the electrostatic energy stored in the system?