Answer:
Given:
q1=8*10-9C
q2=3*10-9C
q3=7*10-9C
S=3m
But electric potential V=kq/r
W=q x change in V
Va=k/r(q1+q2/✓2+q3)
Va=9*10^9/3(8*10^-9+3*10^-9/✓2+7*10^-9)=49.5V
VB=k/0.5r.✓2(q1+q2+q3)
Were r is distance at center given by
r=1/2(r)✓2
VB=9*10^9/0.5*3✓2(8*10^-9+3*10^-9+7*10^-9)=33.9v
Change in = Va-Vb=49.5-33.9=15.6V
Work=r*V=2*10^-9*15.6=3.12×10^-8J