In a concave mirror an erect image will be obtained when the object is placed between pole and focus of the mirror.
Focal length, f = 12 cm
(i) Therefore, the range of object distance is between 0 cm to lt12 cm (from zero to less than 12 cm).
(ii) Image formed will be magnified, i.e., large than the object.
(iii) If the object is placed at 24 cm in front of the mirror, it means that object is placed at 2f, i.e., at the centre of curvature (at C) of the mirror.
The real, inverted and same size (of the object) image will also be formed at 24 cm.