Which one of the following is the stress induced in the bar?

Question

A free bar of length  is heated uniformly from 0⁰C to a temperature  $T^{o}C$ . $\alpha$ is the coefficient of linear expansion and E is the modulus of elasticity. Which one of the following is the stress induced in the bar?

(a) $\frac{\alpha T E}{4}$

(b) $\frac{\alpha T E}{2}$

(c)$\alpha T E$

(d) Zero