Consider the following static route choice problem where 110 vehicles travel from point A to point B. The corresponding travel time (in minutes) of each link is as follows: 

where xi denotes the number of vehicles that choose link i.

Find the number of vehicles that travel on each link whe

a. The user equilibrium condition (UE) is satisfied, where vehicles select the route with the minimum travel time; and 

b. The system optimum condition (SO) is satisfied, where the total travel time is minimised. 

c. Report the total delay savings when satisfying SO instead of UE. 2 4

t = x1 ; t2 = x2 + 20; t3 = x3 + 10; t4 = 3x4