A 1300 kg car coasts on a horizontal road with a speed of 18 m/s

A 1300 kg car coasts on a horizontal road with a speed of 18 m/s? After crossing an unpaved, sandy stretch of road 30.0 m long, its speed decreases to 15 m/s. Useenergy methods to find the magnitude of the average net force on the car in the sandy section.