Computer Science homework help

A 920 kg sports car collides into the rear end of a 2300 kg SUV stopped at a red light. The bumpers lock, the brakes are locked, and the two cars skid forward 3.8 m before stopping. The police officer, knowing that the coefficient of kinetic friction between tires and road is 0.45, calculates the speed of the sports car at impact. What was that speed?