Q$3)$ The rigid bar $AB$ shown is supported by a steel rod $AC$ having a diameter of $20mm$ and an aluminum block having a cross sectional area of $1800mm2.$ The $18mm$ diameter pins at A and $C$ are subjected to single shear. If the failure stress for steel and aluminum are $680$MPa and $70$ MPa, respectively, and the failure shear stress for each pin is $900$MPa, determine the largest load $P$ that can be applied to the bar. Apply a factor of safety of $2\mathrm{.}0.$