Could you give me a whole process of this problem?

15. There are 12 cruise ships scheduled to be in a port for various days during a given week. The ships must be assigned to one of ve different piers (only one ship at a time can be docked at a pier). The question is whether an assignment of ships to piers is possible, given ships' visiting plans. Describe how to make a graph-coloring model of this assignment problem: What are the vertices, what are the edges, what are the colors