$3-$ This year during Christmas you would like to invite your best friend, who recently had a surgery, to come and visit

and celebrate the occasion with you. However, your friend is a student in another country now and does not have lots

of money to pay for costly flight tickets during the peak season. Therefore, you decide to help your friend by paying

a portion of the ticket. Both of you began the search for ticket and draw the graph below showing the routes from

origin $($O$)$ to destination $($D$),$ which is your town. Since your friend had a surgery you prefer to have a shortest flight

time. $($a$)$ If this is a shortest path problem, what acts as distance in this problem? $($b$)$ what is the shortest path and how

long does it take $($please clearly show how you did the calculations for obtaining the answer$).$

$4-$ You and your friend decide to go on a long trip this month around Newfoundland $($you start from your town and

go through all the other towns and then go back home$).$ You live here in St$.$ John's, which we call city $1$ for the sake

of this problem. You sit together and come up with the following distance tables $($all numbers are in miles$)$ with four

destinations, let's call them $2,3,4,$ and $5.$ Formulate an abstract $($or symbolic$)$ linear model which minimizes your

travelled distance while you meet all the four towns and go back home.