Calculating Moment About Axis AC for a Given Force Vector

[Colts]

Homework Statement

http://session.masteringengineering.com/problemAsset/1127287/7/Probs._454_55.jpg
Find the moment about the axis AC. F=<7,12,-6>

Homework Equations

MomentAC = Uac dotted with (Rab X F)
Uac is the unit vector from a to c

The Attempt at a Solution

Uac=<.8,.6,0>
Rab=<4,3,-2>
F=<7,12,-6>
Rab X F =<6,-10,0>
MomentAC=4.8-6
=-1.2
MomentAC*Uac=<-.96,-.72,0>

 

[Colts]

Can anyone help?

 

[Colts]

Anyone?