Consider the following network of one-way streets and intersections. The arrows indicate the direction of traffic flow along the one-way streets, and the numbers refer to the exact number of cars observed to enter or leave the intersections during one minute. Each ; denotes the unknown number of cars which passes along the indicated streets during the same period. 400 B 300 1 500 1000 200 a) (1pt) Write down a linear system corresponding to the flow of traffic in the network. You must explain how you get your equations Do not simply copy the equations implicit in part (b), you will not receive any points if you do this. b) (2pts) The RREF of the system is