A block of mass m = 1 kg, moving on a horizontal surface with speed vi = 2 m s–1 enters a rough patch ranging from x = 0.10 m to x = 2.01 m. The retarding force Fr on the block in this range is inversely proportional to x over this range, F= -k/x for 0.1 2.01 m where k = 0.5 J. What is the final kinetic energy and speed vf of the block as it crosses this patch ?