How does adding weight to the back of a pickup increase the friction between the tires and the icy road?

How does adding weight to the back of a pickup increase the friction between the tires and the icy road?

How does adding weight to the back of a pickup increase the friction between the tires and the icy road? 



A. changes µk
B. changes µs
C. changes R
D. friction is not increased








Answer: C