A round bar of length 
elastic modulus E and Poisson’s ratio 
is subjected to an axial pull ‘P’. What would be the change in volume of the bar?
(a) $\frac{Pl}{\left ( 1-2\mu \right )E}$
(b) $\frac{Pl\left ( 1-2\mu \right )}{E}$
(c) $\frac{Pl\mu }{E}$
(d) $\frac{Pl }{\mu E}$