Answer:
Net flux through the surface is zero.
Step-by-step explanation:
Recall that the net electric flux through a closed surface depends on the net charge enclosed inside that surface.
In our case, there are two point charges of exactly opposite charge (net charge - zero), which are located inside the Gaussian surface of radius "2 a" centered at the origin - both charges are located at a distance "a" from the origin of coordinates, therefore inside the Gaussian surface.
Then the net flux through the surface is also ZERO.