Problem $24-12$ A rigid bar of weight $W-800N$ hangs from three equally

spaced vertical wires $($length $L-150mm,$ spacing $a-50mm)$: two of steel

and one of aluminum. The wires also support a load $P$ acting on the bar. The

diameter of the steel wires is $d_s-2mm,$ and the diameter of the aluminum wire

is $d_s-4mm.$ Assume $E_s=210$GPa and $E_a-70$GPa.

$($a$)$ What load $P_{\text{a}\text{l}\text{l}\text{o}\text{w}}$ can be supported at the midpoint of the bar $(x-a)$ if the

allowable stress in the steel wires is $220$ MPa and in the aluminum wire is

$80$ MPa $?($See figure part a$.)$

$($b$)$ What is $P_{\text{a}\text{l}\text{l}\text{o}\text{w}}$ if the load is positioned at $x-\frac{a}{2}?($See figure part a$.)$

$($c$)$ Repeat $($b$)$ above if the second and third wires are switched as shown in figure

part b$.$