Automobile A, weighing 4000 lb, approaches stationary automobile B, which weighs 2000 lb. 50 feet before collision, A applies its brakes ang goes into a skid. B also has its brakes applied, so it goes into a skid after A rams B. A travels 50 feet after collision and B travels 100 feet after collision. The coeffiecient of kinetic friction between the tires and the road is 0.9. What was the speed of A before its brakes were applied?