The following data are given for the laboratory sample.

$\sigma_0=175$ kPa; $e_0 =1.1$;  $\sigma_0 + \Delta \sigma_0 =300$ kPa; $e=0.9$

If thickness of the clay specimen is $25$ mm, the value of coefficient of volume compressibility is ______ $\times 10^{-4} m^2/kN$