The forces F2 and F3 form a couple The magnitude of the mome
     The forces F_2 and F_3 form a couple. The magnitude of the moment of the couple about the x-axis is:  0 N-m  40 N-m  160 N-m  200 N-m  The total (resultant) moment about point O for the force system shown is:  -30j N-m  -30j + 20k N-m  -30i + 40k N-m  -30j - 40k N-m 
  
  Solution
A) moment = force *distance between two forces
= 20*2 =40 N-m
B) Total moment about O = -(30*1)I + (20*2)K

