A small block with mass 1 kg slides in a vertical circle of radius 0.5 m on the inside of a circular track. There is friction between the track and the block. At the bottom of the block's path, the speed of the block is 5 m/s and at the top of the blocks path, the speed of the block is 1 m/s. In going from the bottom to the top of the track, how much work is done by the friction force on the block?