For the axial structure shown in Figure $3$ :$($a$)$ Draw the axial force diagram $($N$)[-].$Note: You must show the cross$-$sections and your calculations before drawing the diagram.

$($b$)$ Find the maximum stress in compression and the maximum stress in tension.$($

c$)$ Find the displacement of point E relative to point A and its direction. $[$

$($d$)$ What additional force P must be added to point E to ensure that the displacement between E and A $=$ Zero?Note:The structure is made of $2$ materials: steel $($Ea Steel $=190$ GPa$)$ and aluminum $($Ea$=80$ GPa$).$AB and CD have solid circular cross$-$sections with diameter D $($see figure$)$BC and DE have tubular cross$-$sections with external diameter D and tube thickness t $($see figure$)120$ KN $300$ KN

$120$ KN$(1)(2)(3)(4)$Support AFixedDFigure$3$ABBCCDDE

LaB $=1200$ mm

LBc $=600$ mm

LcD $=800$ mm

LDE $=800$ mm

D $=80$ mm

E $=80$ GPa

D $=80$ mm

t $=10$ mm

E $=80$ GPa

D $=40$ mm

E $=190$ GPa

D $=40$ mm

t $=10$ mm

E $=190$ GPa

Support A is fixed, point E is free$-$end