Two sets of students are collecting traffic data at two sections, xx and yy, of a highway 1500 ft apart. Observations at xx show that five vehicles passed that section at intervals of 3, 4, 3, and 5 sec, respectively. If the speeds of the vehicles were 50, 45, 40, 35, and 30 mi/h, respectively, draw a schematic showing the locations of the vehicles 20 sec after the first vehicle passed section xx. Also, determine (a) the time mean speed, (b) the space mean speed, and (c) the density on the highway.