A $2\text{D}$ thin plate with modulus of elasticity, $E=1.0 \mathrm{~N} / \mathrm{m}^{2}$, and Poisson's ratio, $\mu=0.5$, is in plane stress condition. The displacement field in the plate is given by $u=C x^{2} y$ and $v=0$, where $u$ and $v$ are displacements (in $\mathrm{m}$ ) along the $X$ and $Y$ directions, respectively, and $C$ is a constant (in $\mathrm{m}^{-2}$ ). The distances $x$ and $y$ along $X$ and $Y$, respectively, are in $\mathrm{m}$. The stress in the $X$ direction is $\sigma_{X X}=40 x y \mathrm{~N} / \mathrm{m}^{2}$, and the shear stress is $\tau_{X Y}=\alpha x^{2}$ $\mathrm{N} / \mathrm{m}^{2}$. What is the value of $\alpha$ (in $\mathrm{N} / \mathrm{m}^{4}$, in integer)?________________