A roller coaster is traveling along a vertical circular loop (as shown in the following figure). The mass of the coaster is 500 kg. The radius of the loop is 10 m. At the lowest point (Position 1), the speed of the coaster is 25 m/s. When it reaches the highest point (Position 2), its speed reduces to 10 m/s. How much work is done by the frictional force from Position 1 to Position 2?