A 71.9-kg skier coasts up a snow-covered hill that makes an angle of 27.5 ° with the horizontal. The initial speed of the skier is 9.67 m/s. After coasting a distance of 1.50 m up the slope, the speed of the skier is 4.52 m/s. (a) Find the work done by the kinetic frictional force that acts on the skis. (b) What is the magnitude of the kinetic frictional force?