The speed at which the image of the luminous point object is moving, if the luminous point object is moving at speed $v_{0}$ towards a spherical mirror, along its axis, is :
(Given : $R=$ radius of curvature, $u=$ object distance $)$
(a) $v_{t}=-v_{o}$
(b) $v_{t}=-v_{o}\left(\frac{R}{2 u-R}\right)$
(c) $v_{i}=-v_{0}\left(\frac{2 u-R}{R}\right)$
(d) $v_{i}=-v_{o}\left(\frac{R}{2 u-R}\right)^{2}$