A steel rod whose diameter is 6 cm and is 1 m long, experiences heating from temperature $$40^\circ C$$ to $$200^\circ C$$. The coefficient of thermal expansion is $$\alpha = 12 \times 10^{-8} / ^\circ C$$ and Young's modulus is 300 GPa. If the rod has not been restricted in its original position, the thermal stress (MPa) developed is ..............

A

0

B

256

C

288

D

300