18. A 85 kg snowboarder, including his equipment, heads down a ski hill starting at a height of 150 m, with an initial speed of 6.3 km/h above the bottom of the hill. (a) [5 marks] Determine the speed she could attain when she arrives at the bottom of the hill, assuming that there is no drag. friction or any other damping forces. (b) [5 marks] If she only reaches a speed of 90 km/h, what was the percentage of energy lost to kinetic friction? (c) [4 marks] Assuming that all energy lost is due to the kinetic friction between the snowboard and the snow, and assuming that the slushy ice was originally at 0 "C, how much ice would have melted? The specific latent heat of fusion of water is 334 J/g. Please answer to three significant figures. (Hint: Pay attention to unit conversion. This is not a kinematics problem.)