Hey! I am college student and fairly new to Algorithms and Data Structure.
I am struggling with a problem.

The problem is that there a n cities and each pair of city (x,y) have some cost for connecting through highway. We have to find the minimum cost of connecting all cities?
(This part is fairly simple if I am understanding this correctly then kruskal or prim Algo should do here)

The tricky part for me is that some suboptimal choices have already been made (i.e. certain cities already have roads) and we have to design an algorithm to find a cost minimizing road network. connecting every city to built subject to the choices already made.

I would be really grateful if someone can help me out here :)
Not looking for an answer just maybe some direction or link to some resource.