two roads connect an origin-destination pair with performance functions t1=5+(x1/2)^2 and t2=7+(x2/4)^2 ( t is in minutes and x in thousands of vehcles per hour) it is known that at user equilibrium 75% of the origin-destination demand takes route 1. what percentage would take route 1 if a system -optional solution were achieved , and how much travel time would be saved?