A 520 kg rock slides from down a hillside that is 500 m long and 300 m high. the coefficient of kinetic friction between the rock and the hill surface is 0.25. If the gravitational potential energy U of the earth-rock system is 0 at the bottom of the will, what is the value of U just before the slide, how much energy is transferred to the thermal energy during the slide, what is the kinetic energy of the rock as it reaches the bottom of the hill, and what is its speed?