A 200 mm long, stress free rod at room temperature is held between two immovable rigid walls.
The temperature of the rod is uniformly raised by 250$^{^0}C$. If the Young’s modulus and coefficient
of thermal expansion are 200 GPa and $^{1\times 10^-5/^{^0}C}$, respectively, the magnitude of the longitudinal stress (in MPa) developed in the rod is _____________