Assuming a linear speed-density relationship, the mean free-flow speed is observed to be 60 mph near zero density, and the corresponding jam density is about 120 vehicles per mile. a) What is the maximum flow rate (i.e., capacity)? b) Draw the u-k (speed-density) and q-k (flow-density) diagrams and indicate critical values. c) Compute the possible speeds and densities corresponding to a flow rate of 1000 vph, describing traffic conditions from a driver's point of view. d) Compute the average headway and spacing at the maximum flow rate.