A non- isotropic solid metal cube has coefficients of linear expansion as:$5\times {10}^{-5}/{}^{0}C$   along the x-axis and  $5\times {10}^{-6}/{}^{0}C$ along the y and the z-axis. If coefficient of volume expansion of the solid $C\times {10}^{-6}/{}^{0}C$ then the value of C is _________