Two masses are connected by a string which passes over a pulley with negligible mass and friction. One mass hangs vertically and one mass slides on a 30.0-degree incline. The inclined surface has a coefficient of kinetic friction of 0.200. The vertically hanging mass is 4.00 kg and the mass on the incline is 6.00 kg. The acceleration of the 4.00-kg mass is (the initial velocity of the 6.00-kg mass is up the incline)?