Problems $4\mathrm{.}41$ and $4\mathrm{.}42$

Determine the moment of force $F$ about line $AB$ as follows.

$($a$)$ Determine the moment of $F$ about point $A,$vec$(M{)}_A,$ and then determine the component of this moment in the direction of line $AB.$

$($b$)$ Determine the moment of $F$ about point $B,$vec$(M{)}_B,$ and then determine the component of this moment in the direction of line $AB.$

$($c$)$ Comment on differences and$/$or agreement between vec$(M{)}_A,$vec$(M{)}_B,$ and the moment about line $AB$ found in Parts $($a$)$ and $($b$).$ Also comment on the meaning of the sign $($positive or negative$)$ found for the moment about line $AB.$