A 2.1 by 10 to the power of 3 kg car starts from rest at the top of a driveway that is sloped at an angle of 20.0 with the horizontal. An average friction force of 4.0 by 10 to the power of 3 N impedes the cars motion so that the cars speed at the bottom of the driveway is 3.8 meters per seconds. What is the length of the driveway?