$(21$ points$)$ The bar is loaded as shown. Determine the horizontal displacement of end $D$ relative to the wall $A$ if sections $AB,BC,$ and CD are made of $6061-$T$6$ aluminum, $304$ cold rolled stainless steel, and A$-47$ iron, respectively. Assume $P=390N,L=450cm,$ and $d=20mm.$

For $2$ points extra credit on Exam $2,$ what is the maximum normal stress in the rod AD$?$

${}_{\frac{D}{A}}=$

Extra Credit:

${}_{\text{M}\text{a}\text{x}}=$

Section AB $(6061-$T$6$ Aluminum$)$: E $=70$ GPA

Section BC $(302$ cold rolled steel$)$: E$=190$ GPA

Section CD $($A$-47$ iron$)$: E$=165$ GPA