A force of 45.7 N is required to start a 5.0-kg box moving across a horizontal concrete floor. (a) What is the coefficient of static friction between the box and the floor? (b) If the force continues at the same value, the box accelerates at 0.54 m/s^2. What is the coefficient of kinetic friction? I've been able to solve part (a) which turned out to be .933. What am I supposed to do with the acceleration to solve for part (b)?