When the temperature is at $30^{\circ} \mathrm{C}$, the A-36 steel pipe fits snugly between the two fuel tanks. When fuel flows through the pipe, the temperatures at ends $A$ and $B$ rise to $130^{\circ} \mathrm{C}$ and $80^{\circ} \mathrm{C},$ respectively. If the temperature drop along the pipe is linear, determine the average normal stress developed in the pipe. Assume each tank provides a rigid support at $A$ and $B$