A 800-{rm kg} sports car collides into the rear end of a 2300-{rm kg} SUV stopped at a red light. The bumpers lock, the brakes are locked, and the two cars skid forward 2.8 {rm m} before stopping. The police officer, estimating the coefficient of kinetic friction between tires and road to be 0.80, calculates the speed of the sports car at impact.