An object is placed at the zero-mark of a meterstick while its image appears at the +15 cm mark using a convex mirror with a focal length of magnitude |f| = 10 cm. Where is the mirror placed? %3D The mirror is placed at the +10 cm mark of the meterstick. The mirror is placed at the +40 cm mark of the meterstick. The mirror is placed at the +50 cm mark of the meterstick. The mirror is placed at the +20 cm mark of the meterstick. The mirror is placed at the +30 cm mark of the meterstick.