# A metalic ring of radius r and cross sectional area A is fitted into a wooden circular disc of radius $R(R > 1)$. If the Young's modulus of the material of the ring is Y, the force with which the metal ring expands is :

$\begin {array} {1 1} (a)\;\frac{AYR}{r} & \quad (b)\;\frac{AY(R-r)}{r} \\ (c)\;\frac{Y(R-r)}{Ar}a & \quad (d)\;\frac{YR}{AR} \end {array}$

$(B)\;\frac{AY(R-r)}{r}$
Hence B is the correct answer.