Answer:

Step-by-step explanation:
From the question we are told that
Two points charge of 4\mu C and 2\mu C
Generally we find the Va and Vb individually to find there difference
Given a rectangle with two equal sides each,Assume lengths for bot sides
Length L=0.3
Breath B=0.4
Diagonal D=

at opposite sides
Mathematically Va can represented as





Mathematically Vb is represented as





Therefore
