64. A steel ring of radius r and cross-section area ‘A’ is fitted on to a wooden disc of radius R

A steel ring of radius r and cross-section area ‘A’ is fitted on to a wooden disc of radius R(R>r). If Young’s modulus be E, then the force with which the steel ring is expanded is

(a) AE(R/r)                                            (b) AE{(R-r)/r}

(c)   (E/A){(R-r)/A}                             (d) (Er)/(AR)

ANSWER-b