A roller coaster reaches the top of the steepest hill with a speed of 6.8 km/h. It then descends the hill, whi?

A roller coaster reaches the top of the steepest hill with a speed of 6.8 km/h. It then descends the hill, which is at an average angle of 25o and is 55 m long. What will its speed be when it reaches the bottom? ume �k = 0.18.