Moment about a point in an incline plane

[Robb]

Homework Statement

Force F = 460 N acts perpendicular to the inclined plane

Determine the moment produced by F about point A.
Enter the x, y, and z components of the moment separated by commas.

Homework Equations

The Attempt at a Solution

r(CA)=4j-3k
u(CA)=4/5j-3/5k

r(CB)=-3i+4j
u(CB)=-3/5i+4/5j

u(CA) x u(CB)=1.28i+.36j+.48k
F=460(1.28i+.36j+.48k)=589i+166j+221k

r(CA) x F=1382i-1767j-2356k

masteringengineering.com says the answer is wrong. Please help!

 

[Orodruin]

F=460(1.28i+.36j+.48k)=589i+166j+221k

Is the magnitude of this force 460 N?