A box rests on top of a flat bed truck. the box has a mass of m = 18 kg. the coefficient of static friction between the box and truck is μs = 0.86 and the coefficient of kinetic friction between the box and truck is μk = 0.69. 1) the truck accelerates from rest to vf = 16 m/s in t = 16 s (which is slow enough that the box will not slide). what is the acceleration of the box?