Civil Engineering Materials #$1\mathrm{.}11$

The rectangular block shown in figure is subjected to tension within the elastic range. The increase in the length of $a$ is $2{10}^{-3}$ in$.$ and the contraction of $b$ is $3\mathrm{.}25{10}^{-4}$ in$.$ if the original lengths of a and $b$ were $2$ in$.$ and $1$ in$.,$ respectively, what is Poisson's ratio for the material of the specimen?