The two solid steel rods are bolted together along their length. At A the support is fixed pinned. At B there is a roller support. When the beam is loaded as shown in the figure, determine the required diameter of the rods if the allowable stress for bending is given as ${}_{\text{a}\text{l}\text{l}\text{o}\text{w}\text{a}\text{b}\text{l}\text{e}}=130$MPa.

For a circular section, $I=\frac{r^4}{4}.$