Assume you are an observer standing at a point along a three- lane roadway. All vehicles in lane 1 are traveling at 30 mph, all vehicles in lane 2 are traveling at 45 mph, and all vehicles in lane 3 are traveling at 60 mph. There is also a constant spacing of 0.5 miles between vehicles. If you collect spot speed data for all vehicles as they cross your observation point, for 30 minutes, what will be the time-mean speed and space-mean speed for this traffic stream