The structure shown has two forces of magnitude F applied. If F = 421b and the forces are...

The structure shown has two forces of magnitude F applied. If F = 421b and the forces are to be a couple, determine the orientation they should have so that the moment of the couple about line a is as large as possible. Line a has direction angles θx = 72°, θy =36°, and θz= 60°.

Figure P4.58