The structure below consists of two cylindrical rods $\backslash ($ A B $\backslash )$ and $\backslash ($ B C $\backslash )$ that is welded together at $\backslash ($ B $\backslash )$ and fixed to the wall at $\backslash ($ C $\backslash ).$ Rod $\backslash ($ B C $\backslash )$ is a solid rod with diameter of $40\mathrm{.}5$ mm $,$ while $\backslash (\backslash$operatorname$\{$rod$\}$ A B $\backslash )$ is a hollow rod with outer and inner diameter of $30$ mm and $17\mathrm{.}5$ mm respectively.

i$.$ Calculate the average normal stress in $\backslash (\backslash$operatorname$\{$rod$\}$ A B $\backslash ),$

ii$.$ Calculate the average normal stress in $\backslash (\backslash$operatorname$\{$rod$\}$ B C $\backslash ),$ and

iii. Based on your answer in i$.$ and ii$.,$ determine the factor of safety of the structure if rod $\backslash ($ A B $\backslash )$ is made of structural steel $($ASTM$-$A$36)[$see Appendix $1]$ and rod $\backslash ($ B C $\backslash )$ is made of magnesium alloy AZ$80($forging$)[$see Appendix $2].$