On a roller coaster ride the total mass of the cart - with passengers included - is 305 kg. Peak K is at 47.5 m above the ground, peak L is at 28.5 m. The speed of the cart at K is 18.2 m/s, at L it is 12.0 m/s. (The wheel mechanism on roller coaster carts always keeps the carts safely on the rail.)
How much energy is lost due to friction between the two peaks?