Answer:
C - 11.76 N (Newtons)
Step-by-step explanation:
2 steps are needed,
First find the Force being applied by the box on the surface.
F = M(a) [Force equals: mass X Acceleration (of gravity)]
You get 39.2 N of Force.
Plug in the remaining values into the equation for Frictional Force
F(f) = μ(F) [Coefficient of Friction X Force applied by the Box]
So
F(f) = 0.3(39.2) = 11.76 N (of Frictional Force)