13. A person is pushing a box to the right on a horizontal floor at constant speed (the coefficient of static friction between the box and floor is 0.40; the coefficient of kinetic friction is 0.10). The person pushing the box then stops pushing it, and the box slides another 0.15 m before it comes to rest. How fast was the box moving initially? f vi = MR = 0.1 14. AX=.15