A huge box having a mass of 6.80 kg is pulled down along a frictionless surface inclined at 42.0 below the horizontal by a constant force of 7.21 N that is parallel to the incline. The baggage was initially at rest at the top of the ramp and is moving at 5.52 m/s when it reaches the bottom of the ramp. The coefficient of kinetic friction between the box and the inclined surface is 0.39. (a) How much work is done on the box by all forces acting on it? (b) How long is the inclined surface