4. Figure 5 describes a ow of trafc. with the units being . vehicles per hour. (a) Construct a system of linear equations that de scribes this ow. (b) The total time it takes the vehicles to travel any I stretch of road is proportional to the trafc along that stretch. For example, the total time it takes I. ' vehicles to traverse AB is kx. minutes. Assuming that the constant is the same for all sections of road, ' the total time for all 200 vehicles to be in this net- work is kx, + kaz + [\"3 + 210:, + kxs. What is . this total time if k = 4? Give the average time for each car. F x;;_ E rigura 5 Trafc ow in Problem 4