Mechanics, specifically Moment question

[SirMarksAlot]

Homework Statement

Also, I am not entirely sure what the question is exactly asking. Also, what does the line of action represent?

Homework Equations

M = Fx(Perpendicular distance) + Fy(Perpendicular distance)

For couples:

M=Fd

The Attempt at a Solution

i was thinking that i need to find the moment at D, but wouldn't the resultant force still be the same? except located at D? However, since this is a couple, would the moment be the same everywhere?

 

[Quinzio]

A force located at D doesn't give a moment (in D).
You shoud find a force located somewhere else than D.

A hint: the text speaks about LINE of action. Why ?

 

[SirMarksAlot]

Wouldnt the force anywhere still be 48 N since the couple cancels each other out, and leaves only the moment?

Also, is the line of action just the direction/line that the force follows?