There are three routes available to the travellers between a single OD pair. For each case below, you are given the travel time t on each route, as well as the number of travellers x using each route. Select the case that satisfies the principle of user equilibrium.

Question $2$Select one:

a$.$

t$1=40,$ t$2=40,$ and t$3=30,$ while x$1=10,$ x$2=25$ and x$3=0$

b$.$

t$1=25,$ t$2=30,$ and t$3=40,$ while x$1=0,$ x$2=20$ and x$3=25$

c$.$

t$1=40,$ t$2=30,$ and t$3=30,$ while x$1=10,$ x$2=25$ and x$3=0$

d$.$

t$1=20,$ t$2=35,$ and t$3=40,$ while x$1=40,$ x$2=0$ and x$3=0$