What is the net flux through the Gaussian surface in terms of the fields EW and ER and the cross-sectional area A?
a) Φ=EW⋅A+ER⋅A
b) Φ=EW⋅A−ER⋅A
c) Φ=(EW+ER) ⋅A
d) Φ=(EW−ER) ⋅A