1. The problem statement, all variables and given/known data Calculate the magnitude and coordinate angles of the resultant couple moment, caused by the forces. 2. Relevant equations M= r x F 3. The attempt at a solution M3= -0.2* 80k= -16k M2= 0.2* 120i= 24i M1= -0.2*100j= -20j M4= r x F= ? I just can't seem to be able to expres r into a vector, I tried to first determine the coordinates of the ends of the bar on which the tips of the arrows of F4 and -F4 lie. And then use this to calculate the vector that specifies the distance between them. Sadly without succes. Using the geometry to find the coordinates won't work for me.