A solid steel cube constrained on all six faces is heated so that the temperature rises uniformly by
$\left ( \Delta T \right )$. If the thermal coefficient of the material is $\alpha$, young’s modulus is E and the Poisson’s ratio is$\nu$, the thermal stress developed in the cube due to heating is
(a) $-\frac{\alpha (\Delta T)E}{(1-2\upsilon )}$ (b)$-\frac{2\alpha (\Delta T)E}{(1-2\upsilon )}$
(c) $-\frac{3\alpha (\Delta T)E}{(1-2\upsilon )}$ (d) $-\frac{\alpha (\Delta T)E}{3(1-2\upsilon)}$