Question $1(25$ points$)$:

In the figure above, $F$ has the magnitude shown and is applied at point $B.$

$($A$)$ Express $F$ in Cartesian vector form

$($B$)$ Determine vector OB in Cartesian vector form

$($C$)$ Find the moment created at point $O$ when $F$ is applied at point $B.$

Specifically need help with $($C$)$