A point charge $q$ sits on the axis of a flat circular disc, at a distance $d$ from the centre of the disc. The radius of the disc is $\sqrt{3}\,d$, as shown in the figure. The electric flux through the disc is

Fig. 1: A point charge q on the axis of a disc of radius root 3 times d, at a distance d from its centre, with the cone from the charge to the edge of the disc.