A 5 m rod having a uniform cross sectional area of 1000 mm² is secured between two walls 5 m part. The load in the rod is zero at 27°C. E = 200 GPa, α = 11,25 x 10⁻⁶ /°C. When the temperature rise to 57°C, what is the stress in the rod assuming the walls are rigid.

a. 67.5 MPa (T)
b. 67.5 MPa (C)
c. 78.6 MPa (T)
d. 78.6 MPa (C)