$2.$ The rigid pole and cross$-$arm assembly is supported by the three cables shown.

$($a$)$ Determine the equivalent force$-$couple system at point $\backslash ($ O $\backslash ).$

$($b$)$ Determine the vector expression for the moment of the $\backslash (1\mathrm{.}2-\backslash$mathrm$\{$kN$\}\backslash )$ tension about point E and about the line $\backslash ($ A E $\backslash ).$