A steel rod, 100 mm long is held between two rigid supports. It is heated by 20°C. If the coefficient of thermal expansion of the material of the rod is 15 x 10-6 /° C and modulus of elasticity is 200 x 103 MN/m2, what is the stress in the rod ?
A. 20 MN/m2 B. 40 MN/m2 C. 60 MN/m2 D. 80 MN/m2