A group of construction workers are building a house and want to lower down an excess bundle of 1420 kg bricks to ground. They tie one end of a rope to the bundle of bricks, loop it through a pulley, and tie the other end of the rope to a toolbox. If the coefficient of kinetic friction between the toolbox and the floor is 0.690 and the acceleration of the bundle of bricks is 6.20 m/s^2, what is the mass of the toolbox?