According to the rule of 72, in about how many years will $20 dollars be worth $10 if the rate of inflation is 6%

An airplane is flying at an elevation of 5150 ft, directly above a straight highway. two motorists are driving cars on the highway on opposite sides of the plane, and the angle of depression to one car is 35 ̊ and to the other is 52 ̊. how far apart are the cars?