There are three paths between an origin and destination pair $(A,D)$ :

Path $1$: $A-D$

Path $2$: $A-B-D$

Path $3$: $A-B-C-D$

Where, $AB,AD,BD,BC$ and $CD$ are unidirectional links connecting the nodes $($

$A,B,C$ and $D$ in the network. Let, $x_{AB},x_{AD},x_{BD},x_{BC}$ and $x_{CD}$ be the link flows

and $t_{AB},t_{AD},t_{BD},t_{BC}$ and $t_{CD}$ be the trael time of the links given in minutes.

Given,

$t_{AB}=1+x_{AB}$

$t_{AD}=x_{AD}$

$t_{BD}=x_{BD}$

$t_{BC}=28+x_{BC}$

$t_{CD}=1+x_{CD}$

Assuming $28$ of demands between nodes A and $D,$ using the definition of user

equilibrium, report equilibrium path travel time in minutes.

THE CORRECT ANSWER IS $19$