You are trying to slide a refrigerator across a horizontal floor. The mass of the refrigerator is 200 kg, and you need to exert a force of 350 N to make it just begin to move. 

(a) What is the coefficient of static friction between the floor and the refrigerator? 

(b) After it starts moving, the refrigerator reaches a speed of 2.0 m/s after 5.0 s. What is the coefficient of kinetic friction between the refrigerator and the floor?