From the given text, what is the coefficient of kinetic friction if the 8 kg block moves with constant velocity? (g = 10 m/s²)

I - The coefficient of kinetic friction is directly proportional to the force applied to the body.
II - The coefficient of kinetic friction is independent of the relative speed between the body and the surface.
III - The coefficient of kinetic friction is dependent on the nature of the surfaces in contact.
a) Only I is correct.
b) Only II is correct.
c) Only III is correct.
d) I and III are correct.
e) II and III are correct.