Normal force on an 8.0 kg box resting on a level floor

Assumptions: the floor is level, the box is not accelerating vertically, and g = 9.8 m/s^2.
Vertical forces balance, so F_N = mg.
F_N = (8.0 kg)(9.8 m/s^2)
F_N = 78.4 N
The normal force is 78.4 N upward.