If A’ is the image of A then the light ray going from B and hitting the mirror at C will intersect the principal axis at which point?
B'
AB is a erect object. Since the image of A is on the same side and below the principal axis, the image is real and inverted.
This means that the image of AB is A'B'. Now a ray leaving from B should pass through B' after reflection so that image of B is formed at B'. Hence, after reflection the ray will pass through B'.