Physics education research, electronic materials, and the musings of Christopher Moore, Ph.D.

At t = 494 s after midnight, a spacecraft of mass 1340 kg is located at position ‹ 6 × 105, 6 × 105, −7 × 105 › m, and at that time an asteroid whose mass is 2 × 1015 kg is located at position ‹ 4 × 105, −4 × 105, −15 × 105 › m. There are no other objects nearby.  Calculate the vector force acting on the spacecraft. 

I used the equation for the force of gravity on an object, but i keep coming up with the wrong numbers.  Can someone help me?