Afour-lane freeway (two 12-ft wide lanes in each direction) is located on rolling terrain and has a design speed of 70 mph, and no lateral obstructions are within 8 ft of the pavement edges. the traffic stream consists of cars and trucks only (no buses or recreation vehicles). a weekday peak hour volume of 1800 vehicles is observed, with 500 arriving in the most congested 15-minute period. if a level of service no worse than c is desired, determine the maximum number of trucks that can be presented in the peak hour traffic volume.