Perform A$$ search for the above problem formulation using h$1($x$)$

as the heuristic function.

$($a$)(15$ pts$)$ Show all the changes on f rontier until a node containing

a four$-$city partial tour is pulled out from the list. Each entry in

f rontier contains the partial tour and its f $($x$),$ g$($x$),$ h$1($x$)$ values.