An object is placed in front of a concave mirror of focal length f. A virtual image of magnification 2 is formed.How for must the object be moved from original position so that a real image of same size is formed.

Question

$(a)\;f \\ (b)\;\frac{f}{2} \\ (c)\;\frac{3f}{2} \\ (d)\;\frac{2f}{3}$