Rank the Gaussian surfaces as shown in the figure. In order of increasing electric flux, starting with the most negative.

Consider the charge configuration and a spherical Gaussian surface as shown in the figure. Which one of the three charges will be the cause of electric field while calculating the flux over the spherical surface ?

A point charge of 2muC is at the centre of a cubical Gaussian surface 9cm on the edge. Calculate the net electric flux through the surface.