From a photograph one observes that on a level section of highway 20 percent of the vehicles are trucks, 80 percent are cars. and that there are 50 vehicles per mile of highway. The trucks travel at 40 miles'hour, and the cars at 50 miles'hour. This highway also has a section with a steep grade on which the speed of the trucks drops to 20 miles'hour, and the speed of the cars to 40 miles'hour. No vehicles enter or leave the observed sections of the highway (except at the ends). and the flows are stationary. There is no traffic congestion. queuing. or vehicle backup on this highway. Determine the percentage of trucks as seen by a stationary observer on the grade. Show all steps in your solution. In the real mid-term